Finite Math Examples

$x - 3 y + 4 z = 25$ , $y - z + w = - 12$ , $- 2 x + 3 y - 3 z + 3 w = - 18$ , $3 y - 4 z + w = - 29$

Step 1

Move all of the variables to the left side of each equation.

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Step 1.1

Move $- z$ .

$x - 3 y + 4 z = 25$

$y + w - z = - 12$

$- 2 x + 3 y - 3 z + 3 w = - 18$

$3 y - 4 z + w = - 29$

Step 1.2

Reorder $y$ and $w$ .

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$- 2 x + 3 y - 3 z + 3 w = - 18$

$3 y - 4 z + w = - 29$

Step 1.3

Move $- 3 z$ .

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$- 2 x + 3 y + 3 w - 3 z = - 18$

$3 y - 4 z + w = - 29$

Step 1.4

Move $3 y$ .

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$- 2 x + 3 w + 3 y - 3 z = - 18$

$3 y - 4 z + w = - 29$

Step 1.5

Reorder $- 2 x$ and $3 w$ .

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$3 w - 2 x + 3 y - 3 z = - 18$

$3 y - 4 z + w = - 29$

Step 1.6

Move $- 4 z$ .

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$3 w - 2 x + 3 y - 3 z = - 18$

$3 y + w - 4 z = - 29$

Step 1.7

Reorder $3 y$ and $w$ .

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$3 w - 2 x + 3 y - 3 z = - 18$

$w + 3 y - 4 z = - 29$

$x - 3 y + 4 z = 25$

$w + y - z = - 12$

$3 w - 2 x + 3 y - 3 z = - 18$

$w + 3 y - 4 z = - 29$

Step 2

Represent the system of equations in matrix format.

$[\begin{array}{c} 0 & 1 & - 3 & 4 \\ 1 & 0 & 1 & - 1 \\ 3 & - 2 & 3 & - 3 \\ 1 & 0 & 3 & - 4 \end{array}] [\begin{array}{c} w \\ x \\ y \\ z \end{array}] = [\begin{array}{c} 25 \\ - 12 \\ - 18 \\ - 29 \end{array}]$

Step 3

Find the determinant of the coefficient matrix $[\begin{array}{c} 0 & 1 & - 3 & 4 \\ 1 & 0 & 1 & - 1 \\ 3 & - 2 & 3 & - 3 \\ 1 & 0 & 3 & - 4 \end{array}]$ .

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Step 3.1

Write $[\begin{array}{c} 0 & 1 & - 3 & 4 \\ 1 & 0 & 1 & - 1 \\ 3 & - 2 & 3 & - 3 \\ 1 & 0 & 3 & - 4 \end{array}]$ in determinant notation.

$| \begin{array}{c} 0 & 1 & - 3 & 4 \\ 1 & 0 & 1 & - 1 \\ 3 & - 2 & 3 & - 3 \\ 1 & 0 & 3 & - 4 \end{array} |$

Step 3.2

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in column $2$ by its cofactor and add.

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Step 3.2.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + & - \\ - & + & - & + \\ + & - & + & - \\ - & + & - & + \end{array} |$

Step 3.2.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 3.2.3

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$

Step 3.2.4

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$

Step 3.2.5

The minor for $a_{22}$ is the determinant with row $2$ and column $2$ deleted.

$| \begin{array}{c} 0 & - 3 & 4 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$

Step 3.2.6

Multiply element $a_{22}$ by its cofactor.

$0 | \begin{array}{c} 0 & - 3 & 4 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$

Step 3.2.7

The minor for $a_{32}$ is the determinant with row $3$ and column $2$ deleted.

$| \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} |$

Step 3.2.8

Multiply element $a_{32}$ by its cofactor.

$2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} |$

Step 3.2.9

The minor for $a_{42}$ is the determinant with row $4$ and column $2$ deleted.

$| \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 3 & 3 & - 3 \end{array} |$

Step 3.2.10

Multiply element $a_{42}$ by its cofactor.

$0 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 3 & 3 & - 3 \end{array} |$

Step 3.2.11

Add the terms together.

$- 1 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} | + 0 | \begin{array}{c} 0 & - 3 & 4 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} | + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 3 & 3 & - 3 \end{array} |$

Step 3.3

Multiply $0$ by $| \begin{array}{c} 0 & - 3 & 4 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$ .

$- 1 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} | + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 3 & 3 & - 3 \end{array} |$

Step 3.4

Multiply $0$ by $| \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 3 & 3 & - 3 \end{array} |$ .

$- 1 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} | + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5

Evaluate $| \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$ .

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Step 3.5.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 3.5.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 3.5.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 3.5.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$

Step 3.5.1.4

Multiply element $a_{11}$ by its cofactor.

$1 | \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$

Step 3.5.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 3.5.1.6

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 3.5.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 3.5.1.8

Multiply element $a_{13}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 3.5.1.9

Add the terms together.

$- 1 (1 | \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.2

Evaluate $| \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$ .

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Step 3.5.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 (3 \cdot - 4 - 3 \cdot - 3) - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.2.2

Simplify the determinant.

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Step 3.5.2.2.1

Simplify each term.

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Step 3.5.2.2.1.1

Multiply $3$ by $- 4$ .

$- 1 (1 (- 12 - 3 \cdot - 3) - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.2.2.1.2

Multiply $- 3$ by $- 3$ .

$- 1 (1 (- 12 + 9) - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.2.2.2

Add $- 12$ and $9$ .

$- 1 (1 \cdot - 3 - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.3

Evaluate $| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$ .

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Step 3.5.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 \cdot - 3 - 1 (3 \cdot - 4 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.3.2

Simplify the determinant.

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Step 3.5.3.2.1

Simplify each term.

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Step 3.5.3.2.1.1

Multiply $3$ by $- 4$ .

$- 1 (1 \cdot - 3 - 1 (- 12 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.3.2.1.2

Multiply $- 1$ by $- 3$ .

$- 1 (1 \cdot - 3 - 1 (- 12 + 3) - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.3.2.2

Add $- 12$ and $3$ .

$- 1 (1 \cdot - 3 - 1 \cdot - 9 - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.4

Evaluate $| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$ .

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Step 3.5.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 \cdot - 3 - 1 \cdot - 9 - 1 (3 \cdot 3 - 1 \cdot 3)) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.4.2

Simplify the determinant.

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Step 3.5.4.2.1

Simplify each term.

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Step 3.5.4.2.1.1

Multiply $3$ by $3$ .

$- 1 (1 \cdot - 3 - 1 \cdot - 9 - 1 (9 - 1 \cdot 3)) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.4.2.1.2

Multiply $- 1$ by $3$ .

$- 1 (1 \cdot - 3 - 1 \cdot - 9 - 1 (9 - 3)) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.4.2.2

Subtract $3$ from $9$ .

$- 1 (1 \cdot - 3 - 1 \cdot - 9 - 1 \cdot 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.5

Simplify the determinant.

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Step 3.5.5.1

Simplify each term.

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Step 3.5.5.1.1

Multiply $- 3$ by $1$ .

$- 1 (- 3 - 1 \cdot - 9 - 1 \cdot 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.5.1.2

Multiply $- 1$ by $- 9$ .

$- 1 (- 3 + 9 - 1 \cdot 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.5.1.3

Multiply $- 1$ by $6$ .

$- 1 (- 3 + 9 - 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.5.2

Add $- 3$ and $9$ .

$- 1 (6 - 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.5.5.3

Subtract $6$ from $6$ .

$- 1 \cdot 0 + 0 + 2 | \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} | + 0$

Step 3.6

Evaluate $| \begin{array}{c} 0 & - 3 & 4 \\ 1 & 1 & - 1 \\ 1 & 3 & - 4 \end{array} |$ .

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Step 3.6.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 3.6.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 3.6.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 3.6.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} |$

Step 3.6.1.4

Multiply element $a_{11}$ by its cofactor.

$0 | \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} |$

Step 3.6.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} |$

Step 3.6.1.6

Multiply element $a_{12}$ by its cofactor.

$3 | \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} |$

Step 3.6.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |$

Step 3.6.1.8

Multiply element $a_{13}$ by its cofactor.

$4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |$

Step 3.6.1.9

Add the terms together.

$- 1 \cdot 0 + 0 + 2 (0 | \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} | + 3 | \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} | + 4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 3.6.2

Multiply $0$ by $| \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} |$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 | \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} | + 4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 3.6.3

Evaluate $| \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} |$ .

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Step 3.6.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 (1 \cdot - 4 - 1 \cdot - 1) + 4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 3.6.3.2

Simplify the determinant.

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Step 3.6.3.2.1

Simplify each term.

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Step 3.6.3.2.1.1

Multiply $- 4$ by $1$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 (- 4 - 1 \cdot - 1) + 4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 3.6.3.2.1.2

Multiply $- 1$ by $- 1$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 (- 4 + 1) + 4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 3.6.3.2.2

Add $- 4$ and $1$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 \cdot - 3 + 4 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 3.6.4

Evaluate $| \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |$ .

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Step 3.6.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 \cdot - 3 + 4 (1 \cdot 3 - 1 \cdot 1)) + 0$

Step 3.6.4.2

Simplify the determinant.

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Step 3.6.4.2.1

Simplify each term.

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Step 3.6.4.2.1.1

Multiply $3$ by $1$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 \cdot - 3 + 4 (3 - 1 \cdot 1)) + 0$

Step 3.6.4.2.1.2

Multiply $- 1$ by $1$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 \cdot - 3 + 4 (3 - 1)) + 0$

Step 3.6.4.2.2

Subtract $1$ from $3$ .

$- 1 \cdot 0 + 0 + 2 (0 + 3 \cdot - 3 + 4 \cdot 2) + 0$

Step 3.6.5

Simplify the determinant.

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Step 3.6.5.1

Simplify each term.

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Step 3.6.5.1.1

Multiply $3$ by $- 3$ .

$- 1 \cdot 0 + 0 + 2 (0 - 9 + 4 \cdot 2) + 0$

Step 3.6.5.1.2

Multiply $4$ by $2$ .

$- 1 \cdot 0 + 0 + 2 (0 - 9 + 8) + 0$

Step 3.6.5.2

Subtract $9$ from $0$ .

$- 1 \cdot 0 + 0 + 2 (- 9 + 8) + 0$

Step 3.6.5.3

Add $- 9$ and $8$ .

$- 1 \cdot 0 + 0 + 2 \cdot - 1 + 0$

Step 3.7

Simplify the determinant.

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Step 3.7.1

Simplify each term.

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Step 3.7.1.1

Multiply $- 1$ by $0$ .

$0 + 0 + 2 \cdot - 1 + 0$

Step 3.7.1.2

Multiply $2$ by $- 1$ .

$0 + 0 - 2 + 0$

Step 3.7.2

Add $0$ and $0$ .

$0 - 2 + 0$

Step 3.7.3

Subtract $2$ from $0$ .

$- 2 + 0$

Step 3.7.4

Add $- 2$ and $0$ .

$- 2$

$D = - 2$

Step 4

Since the determinant is not $0$ , the system can be solved using Cramer's Rule.

Step 5

Find the value of $w$ by Cramer's Rule, which states that $w = \frac{D_{w}}{D}$ .

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Step 5.1

Replace column $1$ of the coefficient matrix that corresponds to the $w$ -coefficients of the system with $[\begin{array}{c} 25 \\ - 12 \\ - 18 \\ - 29 \end{array}]$ .

$| \begin{array}{c} 25 & 1 & - 3 & 4 \\ - 12 & 0 & 1 & - 1 \\ - 18 & - 2 & 3 & - 3 \\ - 29 & 0 & 3 & - 4 \end{array} |$

Step 5.2

Find the determinant.

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Step 5.2.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in column $2$ by its cofactor and add.

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Step 5.2.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + & - \\ - & + & - & + \\ + & - & + & - \\ - & + & - & + \end{array} |$

Step 5.2.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 5.2.1.3

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$

Step 5.2.1.4

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$

Step 5.2.1.5

The minor for $a_{22}$ is the determinant with row $2$ and column $2$ deleted.

$| \begin{array}{c} 25 & - 3 & 4 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$

Step 5.2.1.6

Multiply element $a_{22}$ by its cofactor.

$0 | \begin{array}{c} 25 & - 3 & 4 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$

Step 5.2.1.7

The minor for $a_{32}$ is the determinant with row $3$ and column $2$ deleted.

$| \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} |$

Step 5.2.1.8

Multiply element $a_{32}$ by its cofactor.

$2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} |$

Step 5.2.1.9

The minor for $a_{42}$ is the determinant with row $4$ and column $2$ deleted.

$| \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \end{array} |$

Step 5.2.1.10

Multiply element $a_{42}$ by its cofactor.

$0 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \end{array} |$

Step 5.2.1.11

Add the terms together.

$- 1 | \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} | + 0 | \begin{array}{c} 25 & - 3 & 4 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} | + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \end{array} |$

Step 5.2.2

Multiply $0$ by $| \begin{array}{c} 25 & - 3 & 4 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$ .

$- 1 | \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} | + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \end{array} |$

Step 5.2.3

Multiply $0$ by $| \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \end{array} |$ .

$- 1 | \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} | + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4

Evaluate $| \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$ .

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Step 5.2.4.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 5.2.4.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 5.2.4.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 5.2.4.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$

Step 5.2.4.1.4

Multiply element $a_{11}$ by its cofactor.

$- 12 | \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$

Step 5.2.4.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$

Step 5.2.4.1.6

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$

Step 5.2.4.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |$

Step 5.2.4.1.8

Multiply element $a_{13}$ by its cofactor.

$- 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |$

Step 5.2.4.1.9

Add the terms together.

$- 1 (- 12 | \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} | - 1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.2

Evaluate $| \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$ .

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Step 5.2.4.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (- 12 (3 \cdot - 4 - 3 \cdot - 3) - 1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.2.2

Simplify the determinant.

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Step 5.2.4.2.2.1

Simplify each term.

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Step 5.2.4.2.2.1.1

Multiply $3$ by $- 4$ .

$- 1 (- 12 (- 12 - 3 \cdot - 3) - 1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.2.2.1.2

Multiply $- 3$ by $- 3$ .

$- 1 (- 12 (- 12 + 9) - 1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.2.2.2

Add $- 12$ and $9$ .

$- 1 (- 12 \cdot - 3 - 1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.3

Evaluate $| \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$ .

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Step 5.2.4.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (- 12 \cdot - 3 - 1 (- 18 \cdot - 4 - (- 29 \cdot - 3)) - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.3.2

Simplify the determinant.

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Step 5.2.4.3.2.1

Simplify each term.

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Step 5.2.4.3.2.1.1

Multiply $- 18$ by $- 4$ .

$- 1 (- 12 \cdot - 3 - 1 (72 - (- 29 \cdot - 3)) - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.3.2.1.2

Multiply $- (- 29 \cdot - 3)$ .

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Step 5.2.4.3.2.1.2.1

Multiply $- 29$ by $- 3$ .

$- 1 (- 12 \cdot - 3 - 1 (72 - 1 \cdot 87) - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.3.2.1.2.2

Multiply $- 1$ by $87$ .

$- 1 (- 12 \cdot - 3 - 1 (72 - 87) - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.3.2.2

Subtract $87$ from $72$ .

$- 1 (- 12 \cdot - 3 - 1 \cdot - 15 - 1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.4

Evaluate $| \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |$ .

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Step 5.2.4.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (- 12 \cdot - 3 - 1 \cdot - 15 - 1 (- 18 \cdot 3 - (- 29 \cdot 3))) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.4.2

Simplify the determinant.

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Step 5.2.4.4.2.1

Simplify each term.

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Step 5.2.4.4.2.1.1

Multiply $- 18$ by $3$ .

$- 1 (- 12 \cdot - 3 - 1 \cdot - 15 - 1 (- 54 - (- 29 \cdot 3))) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.4.2.1.2

Multiply $- (- 29 \cdot 3)$ .

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Step 5.2.4.4.2.1.2.1

Multiply $- 29$ by $3$ .

$- 1 (- 12 \cdot - 3 - 1 \cdot - 15 - 1 (- 54 - - 87)) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.4.2.1.2.2

Multiply $- 1$ by $- 87$ .

$- 1 (- 12 \cdot - 3 - 1 \cdot - 15 - 1 (- 54 + 87)) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.4.2.2

Add $- 54$ and $87$ .

$- 1 (- 12 \cdot - 3 - 1 \cdot - 15 - 1 \cdot 33) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.5

Simplify the determinant.

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Step 5.2.4.5.1

Simplify each term.

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Step 5.2.4.5.1.1

Multiply $- 12$ by $- 3$ .

$- 1 (36 - 1 \cdot - 15 - 1 \cdot 33) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.5.1.2

Multiply $- 1$ by $- 15$ .

$- 1 (36 + 15 - 1 \cdot 33) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.5.1.3

Multiply $- 1$ by $33$ .

$- 1 (36 + 15 - 33) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.5.2

Add $36$ and $15$ .

$- 1 (51 - 33) + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.4.5.3

Subtract $33$ from $51$ .

$- 1 \cdot 18 + 0 + 2 | \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} | + 0$

Step 5.2.5

Evaluate $| \begin{array}{c} 25 & - 3 & 4 \\ - 12 & 1 & - 1 \\ - 29 & 3 & - 4 \end{array} |$ .

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Step 5.2.5.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 5.2.5.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 5.2.5.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 5.2.5.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} |$

Step 5.2.5.1.4

Multiply element $a_{11}$ by its cofactor.

$25 | \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} |$

Step 5.2.5.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} |$

Step 5.2.5.1.6

Multiply element $a_{12}$ by its cofactor.

$3 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} |$

Step 5.2.5.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |$

Step 5.2.5.1.8

Multiply element $a_{13}$ by its cofactor.

$4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |$

Step 5.2.5.1.9

Add the terms together.

$- 1 \cdot 18 + 0 + 2 (25 | \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} | + 3 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} | + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.2

Evaluate $| \begin{array}{c} 1 & - 1 \\ 3 & - 4 \end{array} |$ .

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Step 5.2.5.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot 18 + 0 + 2 (25 (1 \cdot - 4 - 3 \cdot - 1) + 3 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} | + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.2.2

Simplify the determinant.

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Step 5.2.5.2.2.1

Simplify each term.

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Step 5.2.5.2.2.1.1

Multiply $- 4$ by $1$ .

$- 1 \cdot 18 + 0 + 2 (25 (- 4 - 3 \cdot - 1) + 3 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} | + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.2.2.1.2

Multiply $- 3$ by $- 1$ .

$- 1 \cdot 18 + 0 + 2 (25 (- 4 + 3) + 3 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} | + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.2.2.2

Add $- 4$ and $3$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} | + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.3

Evaluate $| \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} |$ .

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Step 5.2.5.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 (- 12 \cdot - 4 - (- 29 \cdot - 1)) + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.3.2

Simplify the determinant.

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Step 5.2.5.3.2.1

Simplify each term.

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Step 5.2.5.3.2.1.1

Multiply $- 12$ by $- 4$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 (48 - (- 29 \cdot - 1)) + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.3.2.1.2

Multiply $- (- 29 \cdot - 1)$ .

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Step 5.2.5.3.2.1.2.1

Multiply $- 29$ by $- 1$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 (48 - 1 \cdot 29) + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.3.2.1.2.2

Multiply $- 1$ by $29$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 (48 - 29) + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.3.2.2

Subtract $29$ from $48$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 \cdot 19 + 4 | \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |) + 0$

Step 5.2.5.4

Evaluate $| \begin{array}{c} - 12 & 1 \\ - 29 & 3 \end{array} |$ .

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Step 5.2.5.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 \cdot 19 + 4 (- 12 \cdot 3 - (- 29 \cdot 1))) + 0$

Step 5.2.5.4.2

Simplify the determinant.

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Step 5.2.5.4.2.1

Simplify each term.

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Step 5.2.5.4.2.1.1

Multiply $- 12$ by $3$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 \cdot 19 + 4 (- 36 - (- 29 \cdot 1))) + 0$

Step 5.2.5.4.2.1.2

Multiply $- (- 29 \cdot 1)$ .

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Step 5.2.5.4.2.1.2.1

Multiply $- 29$ by $1$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 \cdot 19 + 4 (- 36 - - 29)) + 0$

Step 5.2.5.4.2.1.2.2

Multiply $- 1$ by $- 29$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 \cdot 19 + 4 (- 36 + 29)) + 0$

Step 5.2.5.4.2.2

Add $- 36$ and $29$ .

$- 1 \cdot 18 + 0 + 2 (25 \cdot - 1 + 3 \cdot 19 + 4 \cdot - 7) + 0$

Step 5.2.5.5

Simplify the determinant.

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Step 5.2.5.5.1

Simplify each term.

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Step 5.2.5.5.1.1

Multiply $25$ by $- 1$ .

$- 1 \cdot 18 + 0 + 2 (- 25 + 3 \cdot 19 + 4 \cdot - 7) + 0$

Step 5.2.5.5.1.2

Multiply $3$ by $19$ .

$- 1 \cdot 18 + 0 + 2 (- 25 + 57 + 4 \cdot - 7) + 0$

Step 5.2.5.5.1.3

Multiply $4$ by $- 7$ .

$- 1 \cdot 18 + 0 + 2 (- 25 + 57 - 28) + 0$

Step 5.2.5.5.2

Add $- 25$ and $57$ .

$- 1 \cdot 18 + 0 + 2 (32 - 28) + 0$

Step 5.2.5.5.3

Subtract $28$ from $32$ .

$- 1 \cdot 18 + 0 + 2 \cdot 4 + 0$

Step 5.2.6

Simplify the determinant.

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Step 5.2.6.1

Simplify each term.

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Step 5.2.6.1.1

Multiply $- 1$ by $18$ .

$- 18 + 0 + 2 \cdot 4 + 0$

Step 5.2.6.1.2

Multiply $2$ by $4$ .

$- 18 + 0 + 8 + 0$

Step 5.2.6.2

Add $- 18$ and $0$ .

$- 18 + 8 + 0$

Step 5.2.6.3

Add $- 18$ and $8$ .

$- 10 + 0$

Step 5.2.6.4

Add $- 10$ and $0$ .

$- 10$

$D_{w} = - 10$

Step 5.3

Use the formula to solve for $w$ .

$w = \frac{D_{w}}{D}$

Step 5.4

Substitute $- 2$ for $D$ and $- 10$ for $D_{w}$ in the formula.

$w = \frac{- 10}{- 2}$

Step 5.5

Divide $- 10$ by $- 2$ .

$w = 5$

Step 6

Find the value of $x$ by Cramer's Rule, which states that $x = \frac{D_{x}}{D}$ .

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Step 6.1

Replace column $2$ of the coefficient matrix that corresponds to the $x$ -coefficients of the system with $[\begin{array}{c} 25 \\ - 12 \\ - 18 \\ - 29 \end{array}]$ .

$| \begin{array}{c} 0 & 25 & - 3 & 4 \\ 1 & - 12 & 1 & - 1 \\ 3 & - 18 & 3 & - 3 \\ 1 & - 29 & 3 & - 4 \end{array} |$

Step 6.2

Find the determinant.

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Step 6.2.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 6.2.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + & - \\ - & + & - & + \\ + & - & + & - \\ - & + & - & + \end{array} |$

Step 6.2.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 6.2.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$

Step 6.2.1.4

Multiply element $a_{11}$ by its cofactor.

$0 | \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$

Step 6.2.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$

Step 6.2.1.6

Multiply element $a_{12}$ by its cofactor.

$- 25 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$

Step 6.2.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$

Step 6.2.1.8

Multiply element $a_{13}$ by its cofactor.

$- 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$

Step 6.2.1.9

The minor for $a_{14}$ is the determinant with row $1$ and column $4$ deleted.

$| \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.1.10

Multiply element $a_{14}$ by its cofactor.

$- 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.1.11

Add the terms together.

$0 | \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} | - 25 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} | - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.2

Multiply $0$ by $| \begin{array}{c} - 12 & 1 & - 1 \\ - 18 & 3 & - 3 \\ - 29 & 3 & - 4 \end{array} |$ .

$0 - 25 | \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} | - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3

Evaluate $| \begin{array}{c} 1 & 1 & - 1 \\ 3 & 3 & - 3 \\ 1 & 3 & - 4 \end{array} |$ .

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Step 6.2.3.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 6.2.3.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 6.2.3.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 6.2.3.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$

Step 6.2.3.1.4

Multiply element $a_{11}$ by its cofactor.

$1 | \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$

Step 6.2.3.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 6.2.3.1.6

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 6.2.3.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 6.2.3.1.8

Multiply element $a_{13}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 6.2.3.1.9

Add the terms together.

$0 - 25 (1 | \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.2

Evaluate $| \begin{array}{c} 3 & - 3 \\ 3 & - 4 \end{array} |$ .

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Step 6.2.3.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 (1 (3 \cdot - 4 - 3 \cdot - 3) - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.2.2

Simplify the determinant.

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Step 6.2.3.2.2.1

Simplify each term.

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Step 6.2.3.2.2.1.1

Multiply $3$ by $- 4$ .

$0 - 25 (1 (- 12 - 3 \cdot - 3) - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.2.2.1.2

Multiply $- 3$ by $- 3$ .

$0 - 25 (1 (- 12 + 9) - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.2.2.2

Add $- 12$ and $9$ .

$0 - 25 (1 \cdot - 3 - 1 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.3

Evaluate $| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$ .

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Step 6.2.3.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 (1 \cdot - 3 - 1 (3 \cdot - 4 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.3.2

Simplify the determinant.

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Step 6.2.3.3.2.1

Simplify each term.

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Step 6.2.3.3.2.1.1

Multiply $3$ by $- 4$ .

$0 - 25 (1 \cdot - 3 - 1 (- 12 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.3.2.1.2

Multiply $- 1$ by $- 3$ .

$0 - 25 (1 \cdot - 3 - 1 (- 12 + 3) - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.3.2.2

Add $- 12$ and $3$ .

$0 - 25 (1 \cdot - 3 - 1 \cdot - 9 - 1 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.4

Evaluate $| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$ .

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Step 6.2.3.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 (1 \cdot - 3 - 1 \cdot - 9 - 1 (3 \cdot 3 - 1 \cdot 3)) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.4.2

Simplify the determinant.

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Step 6.2.3.4.2.1

Simplify each term.

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Step 6.2.3.4.2.1.1

Multiply $3$ by $3$ .

$0 - 25 (1 \cdot - 3 - 1 \cdot - 9 - 1 (9 - 1 \cdot 3)) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.4.2.1.2

Multiply $- 1$ by $3$ .

$0 - 25 (1 \cdot - 3 - 1 \cdot - 9 - 1 (9 - 3)) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.4.2.2

Subtract $3$ from $9$ .

$0 - 25 (1 \cdot - 3 - 1 \cdot - 9 - 1 \cdot 6) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.5

Simplify the determinant.

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Step 6.2.3.5.1

Simplify each term.

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Step 6.2.3.5.1.1

Multiply $- 3$ by $1$ .

$0 - 25 (- 3 - 1 \cdot - 9 - 1 \cdot 6) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.5.1.2

Multiply $- 1$ by $- 9$ .

$0 - 25 (- 3 + 9 - 1 \cdot 6) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.5.1.3

Multiply $- 1$ by $6$ .

$0 - 25 (- 3 + 9 - 6) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.5.2

Add $- 3$ and $9$ .

$0 - 25 (6 - 6) - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.3.5.3

Subtract $6$ from $6$ .

$0 - 25 \cdot 0 - 3 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4

Evaluate $| \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$ .

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Step 6.2.4.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 6.2.4.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 6.2.4.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 6.2.4.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$

Step 6.2.4.1.4

Multiply element $a_{11}$ by its cofactor.

$1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$

Step 6.2.4.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 6.2.4.1.6

Multiply element $a_{12}$ by its cofactor.

$12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 6.2.4.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 6.2.4.1.8

Multiply element $a_{13}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 6.2.4.1.9

Add the terms together.

$0 - 25 \cdot 0 - 3 (1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.2

Evaluate $| \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$ .

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Step 6.2.4.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 \cdot 0 - 3 (1 (- 18 \cdot - 4 - (- 29 \cdot - 3)) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.2.2

Simplify the determinant.

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Step 6.2.4.2.2.1

Simplify each term.

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Step 6.2.4.2.2.1.1

Multiply $- 18$ by $- 4$ .

$0 - 25 \cdot 0 - 3 (1 (72 - (- 29 \cdot - 3)) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.2.2.1.2

Multiply $- (- 29 \cdot - 3)$ .

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Step 6.2.4.2.2.1.2.1

Multiply $- 29$ by $- 3$ .

$0 - 25 \cdot 0 - 3 (1 (72 - 1 \cdot 87) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.2.2.1.2.2

Multiply $- 1$ by $87$ .

$0 - 25 \cdot 0 - 3 (1 (72 - 87) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.2.2.2

Subtract $87$ from $72$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.3

Evaluate $| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$ .

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Step 6.2.4.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 (3 \cdot - 4 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.3.2

Simplify the determinant.

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Step 6.2.4.3.2.1

Simplify each term.

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Step 6.2.4.3.2.1.1

Multiply $3$ by $- 4$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 (- 12 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.3.2.1.2

Multiply $- 1$ by $- 3$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 (- 12 + 3) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.3.2.2

Add $- 12$ and $3$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 \cdot - 9 - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.4

Evaluate $| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$ .

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Step 6.2.4.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 \cdot - 9 - 1 (3 \cdot - 29 - 1 \cdot - 18)) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.4.2

Simplify the determinant.

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Step 6.2.4.4.2.1

Simplify each term.

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Step 6.2.4.4.2.1.1

Multiply $3$ by $- 29$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 \cdot - 9 - 1 (- 87 - 1 \cdot - 18)) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.4.2.1.2

Multiply $- 1$ by $- 18$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 \cdot - 9 - 1 (- 87 + 18)) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.4.2.2

Add $- 87$ and $18$ .

$0 - 25 \cdot 0 - 3 (1 \cdot - 15 + 12 \cdot - 9 - 1 \cdot - 69) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.5

Simplify the determinant.

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Step 6.2.4.5.1

Simplify each term.

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Step 6.2.4.5.1.1

Multiply $- 15$ by $1$ .

$0 - 25 \cdot 0 - 3 (- 15 + 12 \cdot - 9 - 1 \cdot - 69) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.5.1.2

Multiply $12$ by $- 9$ .

$0 - 25 \cdot 0 - 3 (- 15 - 108 - 1 \cdot - 69) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.5.1.3

Multiply $- 1$ by $- 69$ .

$0 - 25 \cdot 0 - 3 (- 15 - 108 + 69) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.5.2

Subtract $108$ from $- 15$ .

$0 - 25 \cdot 0 - 3 (- 123 + 69) - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.4.5.3

Add $- 123$ and $69$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 | \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$

Step 6.2.5

Evaluate $| \begin{array}{c} 1 & - 12 & 1 \\ 3 & - 18 & 3 \\ 1 & - 29 & 3 \end{array} |$ .

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Step 6.2.5.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 6.2.5.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 6.2.5.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 6.2.5.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |$

Step 6.2.5.1.4

Multiply element $a_{11}$ by its cofactor.

$1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |$

Step 6.2.5.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 6.2.5.1.6

Multiply element $a_{12}$ by its cofactor.

$12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 6.2.5.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 6.2.5.1.8

Multiply element $a_{13}$ by its cofactor.

$1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 6.2.5.1.9

Add the terms together.

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 | \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} | + 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} | + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.2

Evaluate $| \begin{array}{c} - 18 & 3 \\ - 29 & 3 \end{array} |$ .

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Step 6.2.5.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 (- 18 \cdot 3 - (- 29 \cdot 3)) + 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} | + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.2.2

Simplify the determinant.

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Step 6.2.5.2.2.1

Simplify each term.

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Step 6.2.5.2.2.1.1

Multiply $- 18$ by $3$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 (- 54 - (- 29 \cdot 3)) + 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} | + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.2.2.1.2

Multiply $- (- 29 \cdot 3)$ .

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Step 6.2.5.2.2.1.2.1

Multiply $- 29$ by $3$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 (- 54 - - 87) + 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} | + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.2.2.1.2.2

Multiply $- 1$ by $- 87$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 (- 54 + 87) + 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} | + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.2.2.2

Add $- 54$ and $87$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} | + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.3

Evaluate $| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$ .

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Step 6.2.5.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 (3 \cdot 3 - 1 \cdot 3) + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.3.2

Simplify the determinant.

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Step 6.2.5.3.2.1

Simplify each term.

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Step 6.2.5.3.2.1.1

Multiply $3$ by $3$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 (9 - 1 \cdot 3) + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.3.2.1.2

Multiply $- 1$ by $3$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 (9 - 3) + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.3.2.2

Subtract $3$ from $9$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 \cdot 6 + 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |)$

Step 6.2.5.4

Evaluate $| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$ .

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Step 6.2.5.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 \cdot 6 + 1 (3 \cdot - 29 - 1 \cdot - 18))$

Step 6.2.5.4.2

Simplify the determinant.

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Step 6.2.5.4.2.1

Simplify each term.

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Step 6.2.5.4.2.1.1

Multiply $3$ by $- 29$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 \cdot 6 + 1 (- 87 - 1 \cdot - 18))$

Step 6.2.5.4.2.1.2

Multiply $- 1$ by $- 18$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 \cdot 6 + 1 (- 87 + 18))$

Step 6.2.5.4.2.2

Add $- 87$ and $18$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (1 \cdot 33 + 12 \cdot 6 + 1 \cdot - 69)$

Step 6.2.5.5

Simplify the determinant.

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Step 6.2.5.5.1

Simplify each term.

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Step 6.2.5.5.1.1

Multiply $33$ by $1$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (33 + 12 \cdot 6 + 1 \cdot - 69)$

Step 6.2.5.5.1.2

Multiply $12$ by $6$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (33 + 72 + 1 \cdot - 69)$

Step 6.2.5.5.1.3

Multiply $- 69$ by $1$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (33 + 72 - 69)$

Step 6.2.5.5.2

Add $33$ and $72$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 (105 - 69)$

Step 6.2.5.5.3

Subtract $69$ from $105$ .

$0 - 25 \cdot 0 - 3 \cdot - 54 - 4 \cdot 36$

Step 6.2.6

Simplify the determinant.

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Step 6.2.6.1

Simplify each term.

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Step 6.2.6.1.1

Multiply $- 25$ by $0$ .

$0 + 0 - 3 \cdot - 54 - 4 \cdot 36$

Step 6.2.6.1.2

Multiply $- 3$ by $- 54$ .

$0 + 0 + 162 - 4 \cdot 36$

Step 6.2.6.1.3

Multiply $- 4$ by $36$ .

$0 + 0 + 162 - 144$

Step 6.2.6.2

Add $0$ and $0$ .

$0 + 162 - 144$

Step 6.2.6.3

Add $0$ and $162$ .

$162 - 144$

Step 6.2.6.4

Subtract $144$ from $162$ .

$18$

$D_{x} = 18$

Step 6.3

Use the formula to solve for $x$ .

$x = \frac{D_{x}}{D}$

Step 6.4

Substitute $- 2$ for $D$ and $18$ for $D_{x}$ in the formula.

$x = \frac{18}{- 2}$

Step 6.5

Divide $18$ by $- 2$ .

$x = - 9$

Step 7

Find the value of $y$ by Cramer's Rule, which states that $y = \frac{D_{y}}{D}$ .

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Step 7.1

Replace column $3$ of the coefficient matrix that corresponds to the $y$ -coefficients of the system with $[\begin{array}{c} 25 \\ - 12 \\ - 18 \\ - 29 \end{array}]$ .

$| \begin{array}{c} 0 & 1 & 25 & 4 \\ 1 & 0 & - 12 & - 1 \\ 3 & - 2 & - 18 & - 3 \\ 1 & 0 & - 29 & - 4 \end{array} |$

Step 7.2

Find the determinant.

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Step 7.2.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in column $2$ by its cofactor and add.

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Step 7.2.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + & - \\ - & + & - & + \\ + & - & + & - \\ - & + & - & + \end{array} |$

Step 7.2.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 7.2.1.3

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$

Step 7.2.1.4

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$

Step 7.2.1.5

The minor for $a_{22}$ is the determinant with row $2$ and column $2$ deleted.

$| \begin{array}{c} 0 & 25 & 4 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$

Step 7.2.1.6

Multiply element $a_{22}$ by its cofactor.

$0 | \begin{array}{c} 0 & 25 & 4 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$

Step 7.2.1.7

The minor for $a_{32}$ is the determinant with row $3$ and column $2$ deleted.

$| \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} |$

Step 7.2.1.8

Multiply element $a_{32}$ by its cofactor.

$2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} |$

Step 7.2.1.9

The minor for $a_{42}$ is the determinant with row $4$ and column $2$ deleted.

$| \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \end{array} |$

Step 7.2.1.10

Multiply element $a_{42}$ by its cofactor.

$0 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \end{array} |$

Step 7.2.1.11

Add the terms together.

$- 1 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | + 0 | \begin{array}{c} 0 & 25 & 4 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \end{array} |$

Step 7.2.2

Multiply $0$ by $| \begin{array}{c} 0 & 25 & 4 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$ .

$- 1 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \end{array} |$

Step 7.2.3

Multiply $0$ by $| \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \end{array} |$ .

$- 1 | \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} | + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4

Evaluate $| \begin{array}{c} 1 & - 12 & - 1 \\ 3 & - 18 & - 3 \\ 1 & - 29 & - 4 \end{array} |$ .

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Step 7.2.4.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 7.2.4.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 7.2.4.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 7.2.4.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$

Step 7.2.4.1.4

Multiply element $a_{11}$ by its cofactor.

$1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$

Step 7.2.4.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 7.2.4.1.6

Multiply element $a_{12}$ by its cofactor.

$12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$

Step 7.2.4.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 7.2.4.1.8

Multiply element $a_{13}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 7.2.4.1.9

Add the terms together.

$- 1 (1 | \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} | + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.2

Evaluate $| \begin{array}{c} - 18 & - 3 \\ - 29 & - 4 \end{array} |$ .

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Step 7.2.4.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 (- 18 \cdot - 4 - (- 29 \cdot - 3)) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.2.2

Simplify the determinant.

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Step 7.2.4.2.2.1

Simplify each term.

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Step 7.2.4.2.2.1.1

Multiply $- 18$ by $- 4$ .

$- 1 (1 (72 - (- 29 \cdot - 3)) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.2.2.1.2

Multiply $- (- 29 \cdot - 3)$ .

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Step 7.2.4.2.2.1.2.1

Multiply $- 29$ by $- 3$ .

$- 1 (1 (72 - 1 \cdot 87) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.2.2.1.2.2

Multiply $- 1$ by $87$ .

$- 1 (1 (72 - 87) + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.2.2.2

Subtract $87$ from $72$ .

$- 1 (1 \cdot - 15 + 12 | \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.3

Evaluate $| \begin{array}{c} 3 & - 3 \\ 1 & - 4 \end{array} |$ .

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Step 7.2.4.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 \cdot - 15 + 12 (3 \cdot - 4 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.3.2

Simplify the determinant.

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Step 7.2.4.3.2.1

Simplify each term.

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Step 7.2.4.3.2.1.1

Multiply $3$ by $- 4$ .

$- 1 (1 \cdot - 15 + 12 (- 12 - 1 \cdot - 3) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.3.2.1.2

Multiply $- 1$ by $- 3$ .

$- 1 (1 \cdot - 15 + 12 (- 12 + 3) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.3.2.2

Add $- 12$ and $3$ .

$- 1 (1 \cdot - 15 + 12 \cdot - 9 - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.4

Evaluate $| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$ .

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Step 7.2.4.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 \cdot - 15 + 12 \cdot - 9 - 1 (3 \cdot - 29 - 1 \cdot - 18)) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.4.2

Simplify the determinant.

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Step 7.2.4.4.2.1

Simplify each term.

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Step 7.2.4.4.2.1.1

Multiply $3$ by $- 29$ .

$- 1 (1 \cdot - 15 + 12 \cdot - 9 - 1 (- 87 - 1 \cdot - 18)) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.4.2.1.2

Multiply $- 1$ by $- 18$ .

$- 1 (1 \cdot - 15 + 12 \cdot - 9 - 1 (- 87 + 18)) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.4.2.2

Add $- 87$ and $18$ .

$- 1 (1 \cdot - 15 + 12 \cdot - 9 - 1 \cdot - 69) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.5

Simplify the determinant.

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Step 7.2.4.5.1

Simplify each term.

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Step 7.2.4.5.1.1

Multiply $- 15$ by $1$ .

$- 1 (- 15 + 12 \cdot - 9 - 1 \cdot - 69) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.5.1.2

Multiply $12$ by $- 9$ .

$- 1 (- 15 - 108 - 1 \cdot - 69) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.5.1.3

Multiply $- 1$ by $- 69$ .

$- 1 (- 15 - 108 + 69) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.5.2

Subtract $108$ from $- 15$ .

$- 1 (- 123 + 69) + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.4.5.3

Add $- 123$ and $69$ .

$- 1 \cdot - 54 + 0 + 2 | \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} | + 0$

Step 7.2.5

Evaluate $| \begin{array}{c} 0 & 25 & 4 \\ 1 & - 12 & - 1 \\ 1 & - 29 & - 4 \end{array} |$ .

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Step 7.2.5.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 7.2.5.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 7.2.5.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 7.2.5.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} |$

Step 7.2.5.1.4

Multiply element $a_{11}$ by its cofactor.

$0 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} |$

Step 7.2.5.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} |$

Step 7.2.5.1.6

Multiply element $a_{12}$ by its cofactor.

$- 25 | \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} |$

Step 7.2.5.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |$

Step 7.2.5.1.8

Multiply element $a_{13}$ by its cofactor.

$4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |$

Step 7.2.5.1.9

Add the terms together.

$- 1 \cdot - 54 + 0 + 2 (0 | \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} | - 25 | \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} | + 4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |) + 0$

Step 7.2.5.2

Multiply $0$ by $| \begin{array}{c} - 12 & - 1 \\ - 29 & - 4 \end{array} |$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 | \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} | + 4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |) + 0$

Step 7.2.5.3

Evaluate $| \begin{array}{c} 1 & - 1 \\ 1 & - 4 \end{array} |$ .

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Step 7.2.5.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 (1 \cdot - 4 - 1 \cdot - 1) + 4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |) + 0$

Step 7.2.5.3.2

Simplify the determinant.

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Step 7.2.5.3.2.1

Simplify each term.

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Step 7.2.5.3.2.1.1

Multiply $- 4$ by $1$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 (- 4 - 1 \cdot - 1) + 4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |) + 0$

Step 7.2.5.3.2.1.2

Multiply $- 1$ by $- 1$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 (- 4 + 1) + 4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |) + 0$

Step 7.2.5.3.2.2

Add $- 4$ and $1$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 \cdot - 3 + 4 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |) + 0$

Step 7.2.5.4

Evaluate $| \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |$ .

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Step 7.2.5.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 \cdot - 3 + 4 (1 \cdot - 29 - 1 \cdot - 12)) + 0$

Step 7.2.5.4.2

Simplify the determinant.

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Step 7.2.5.4.2.1

Simplify each term.

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Step 7.2.5.4.2.1.1

Multiply $- 29$ by $1$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 \cdot - 3 + 4 (- 29 - 1 \cdot - 12)) + 0$

Step 7.2.5.4.2.1.2

Multiply $- 1$ by $- 12$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 \cdot - 3 + 4 (- 29 + 12)) + 0$

Step 7.2.5.4.2.2

Add $- 29$ and $12$ .

$- 1 \cdot - 54 + 0 + 2 (0 - 25 \cdot - 3 + 4 \cdot - 17) + 0$

Step 7.2.5.5

Simplify the determinant.

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Step 7.2.5.5.1

Simplify each term.

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Step 7.2.5.5.1.1

Multiply $- 25$ by $- 3$ .

$- 1 \cdot - 54 + 0 + 2 (0 + 75 + 4 \cdot - 17) + 0$

Step 7.2.5.5.1.2

Multiply $4$ by $- 17$ .

$- 1 \cdot - 54 + 0 + 2 (0 + 75 - 68) + 0$

Step 7.2.5.5.2

Add $0$ and $75$ .

$- 1 \cdot - 54 + 0 + 2 (75 - 68) + 0$

Step 7.2.5.5.3

Subtract $68$ from $75$ .

$- 1 \cdot - 54 + 0 + 2 \cdot 7 + 0$

Step 7.2.6

Simplify the determinant.

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Step 7.2.6.1

Simplify each term.

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Step 7.2.6.1.1

Multiply $- 1$ by $- 54$ .

$54 + 0 + 2 \cdot 7 + 0$

Step 7.2.6.1.2

Multiply $2$ by $7$ .

$54 + 0 + 14 + 0$

Step 7.2.6.2

Add $54$ and $0$ .

$54 + 14 + 0$

Step 7.2.6.3

Add $54$ and $14$ .

$68 + 0$

Step 7.2.6.4

Add $68$ and $0$ .

$68$

$D_{y} = 68$

Step 7.3

Use the formula to solve for $y$ .

$y = \frac{D_{y}}{D}$

Step 7.4

Substitute $- 2$ for $D$ and $68$ for $D_{y}$ in the formula.

$y = \frac{68}{- 2}$

Step 7.5

Divide $68$ by $- 2$ .

$y = - 34$

Step 8

Find the value of $z$ by Cramer's Rule, which states that $z = \frac{D_{z}}{D}$ .

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Step 8.1

Replace column $4$ of the coefficient matrix that corresponds to the $z$ -coefficients of the system with $[\begin{array}{c} 25 \\ - 12 \\ - 18 \\ - 29 \end{array}]$ .

$| \begin{array}{c} 0 & 1 & - 3 & 25 \\ 1 & 0 & 1 & - 12 \\ 3 & - 2 & 3 & - 18 \\ 1 & 0 & 3 & - 29 \end{array} |$

Step 8.2

Find the determinant.

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Step 8.2.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in column $2$ by its cofactor and add.

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Step 8.2.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + & - \\ - & + & - & + \\ + & - & + & - \\ - & + & - & + \end{array} |$

Step 8.2.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 8.2.1.3

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & 1 & - 12 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} |$

Step 8.2.1.4

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} 1 & 1 & - 12 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} |$

Step 8.2.1.5

The minor for $a_{22}$ is the determinant with row $2$ and column $2$ deleted.

$| \begin{array}{c} 0 & - 3 & 25 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} |$

Step 8.2.1.6

Multiply element $a_{22}$ by its cofactor.

$0 | \begin{array}{c} 0 & - 3 & 25 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} |$

Step 8.2.1.7

The minor for $a_{32}$ is the determinant with row $3$ and column $2$ deleted.

$| \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} |$

Step 8.2.1.8

Multiply element $a_{32}$ by its cofactor.

$2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} |$

Step 8.2.1.9

The minor for $a_{42}$ is the determinant with row $4$ and column $2$ deleted.

$| \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 3 & 3 & - 18 \end{array} |$

Step 8.2.1.10

Multiply element $a_{42}$ by its cofactor.

$0 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 3 & 3 & - 18 \end{array} |$

Step 8.2.1.11

Add the terms together.

$- 1 | \begin{array}{c} 1 & 1 & - 12 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} | + 0 | \begin{array}{c} 0 & - 3 & 25 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} | + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 3 & 3 & - 18 \end{array} |$

Step 8.2.2

Multiply $0$ by $| \begin{array}{c} 0 & - 3 & 25 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} |$ .

$- 1 | \begin{array}{c} 1 & 1 & - 12 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} | + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 3 & 3 & - 18 \end{array} |$

Step 8.2.3

Multiply $0$ by $| \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 3 & 3 & - 18 \end{array} |$ .

$- 1 | \begin{array}{c} 1 & 1 & - 12 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} | + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4

Evaluate $| \begin{array}{c} 1 & 1 & - 12 \\ 3 & 3 & - 18 \\ 1 & 3 & - 29 \end{array} |$ .

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Step 8.2.4.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 8.2.4.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 8.2.4.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 8.2.4.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 3 & - 18 \\ 3 & - 29 \end{array} |$

Step 8.2.4.1.4

Multiply element $a_{11}$ by its cofactor.

$1 | \begin{array}{c} 3 & - 18 \\ 3 & - 29 \end{array} |$

Step 8.2.4.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 8.2.4.1.6

Multiply element $a_{12}$ by its cofactor.

$- 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$

Step 8.2.4.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 8.2.4.1.8

Multiply element $a_{13}$ by its cofactor.

$- 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$

Step 8.2.4.1.9

Add the terms together.

$- 1 (1 | \begin{array}{c} 3 & - 18 \\ 3 & - 29 \end{array} | - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} | - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.2

Evaluate $| \begin{array}{c} 3 & - 18 \\ 3 & - 29 \end{array} |$ .

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Step 8.2.4.2.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 (3 \cdot - 29 - 3 \cdot - 18) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} | - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.2.2

Simplify the determinant.

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Step 8.2.4.2.2.1

Simplify each term.

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Step 8.2.4.2.2.1.1

Multiply $3$ by $- 29$ .

$- 1 (1 (- 87 - 3 \cdot - 18) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} | - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.2.2.1.2

Multiply $- 3$ by $- 18$ .

$- 1 (1 (- 87 + 54) - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} | - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.2.2.2

Add $- 87$ and $54$ .

$- 1 (1 \cdot - 33 - 1 | \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} | - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.3

Evaluate $| \begin{array}{c} 3 & - 18 \\ 1 & - 29 \end{array} |$ .

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Step 8.2.4.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 \cdot - 33 - 1 (3 \cdot - 29 - 1 \cdot - 18) - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.3.2

Simplify the determinant.

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Step 8.2.4.3.2.1

Simplify each term.

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Step 8.2.4.3.2.1.1

Multiply $3$ by $- 29$ .

$- 1 (1 \cdot - 33 - 1 (- 87 - 1 \cdot - 18) - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.3.2.1.2

Multiply $- 1$ by $- 18$ .

$- 1 (1 \cdot - 33 - 1 (- 87 + 18) - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.3.2.2

Add $- 87$ and $18$ .

$- 1 (1 \cdot - 33 - 1 \cdot - 69 - 12 | \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.4

Evaluate $| \begin{array}{c} 3 & 3 \\ 1 & 3 \end{array} |$ .

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Step 8.2.4.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 (1 \cdot - 33 - 1 \cdot - 69 - 12 (3 \cdot 3 - 1 \cdot 3)) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.4.2

Simplify the determinant.

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Step 8.2.4.4.2.1

Simplify each term.

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Step 8.2.4.4.2.1.1

Multiply $3$ by $3$ .

$- 1 (1 \cdot - 33 - 1 \cdot - 69 - 12 (9 - 1 \cdot 3)) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.4.2.1.2

Multiply $- 1$ by $3$ .

$- 1 (1 \cdot - 33 - 1 \cdot - 69 - 12 (9 - 3)) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.4.2.2

Subtract $3$ from $9$ .

$- 1 (1 \cdot - 33 - 1 \cdot - 69 - 12 \cdot 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.5

Simplify the determinant.

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Step 8.2.4.5.1

Simplify each term.

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Step 8.2.4.5.1.1

Multiply $- 33$ by $1$ .

$- 1 (- 33 - 1 \cdot - 69 - 12 \cdot 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.5.1.2

Multiply $- 1$ by $- 69$ .

$- 1 (- 33 + 69 - 12 \cdot 6) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.5.1.3

Multiply $- 12$ by $6$ .

$- 1 (- 33 + 69 - 72) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.5.2

Add $- 33$ and $69$ .

$- 1 (36 - 72) + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.4.5.3

Subtract $72$ from $36$ .

$- 1 \cdot - 36 + 0 + 2 | \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} | + 0$

Step 8.2.5

Evaluate $| \begin{array}{c} 0 & - 3 & 25 \\ 1 & 1 & - 12 \\ 1 & 3 & - 29 \end{array} |$ .

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Step 8.2.5.1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 8.2.5.1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 8.2.5.1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 8.2.5.1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} 1 & - 12 \\ 3 & - 29 \end{array} |$

Step 8.2.5.1.4

Multiply element $a_{11}$ by its cofactor.

$0 | \begin{array}{c} 1 & - 12 \\ 3 & - 29 \end{array} |$

Step 8.2.5.1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |$

Step 8.2.5.1.6

Multiply element $a_{12}$ by its cofactor.

$3 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |$

Step 8.2.5.1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |$

Step 8.2.5.1.8

Multiply element $a_{13}$ by its cofactor.

$25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |$

Step 8.2.5.1.9

Add the terms together.

$- 1 \cdot - 36 + 0 + 2 (0 | \begin{array}{c} 1 & - 12 \\ 3 & - 29 \end{array} | + 3 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} | + 25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 8.2.5.2

Multiply $0$ by $| \begin{array}{c} 1 & - 12 \\ 3 & - 29 \end{array} |$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 | \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} | + 25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 8.2.5.3

Evaluate $| \begin{array}{c} 1 & - 12 \\ 1 & - 29 \end{array} |$ .

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Step 8.2.5.3.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 (1 \cdot - 29 - 1 \cdot - 12) + 25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 8.2.5.3.2

Simplify the determinant.

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Step 8.2.5.3.2.1

Simplify each term.

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Step 8.2.5.3.2.1.1

Multiply $- 29$ by $1$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 (- 29 - 1 \cdot - 12) + 25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 8.2.5.3.2.1.2

Multiply $- 1$ by $- 12$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 (- 29 + 12) + 25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 8.2.5.3.2.2

Add $- 29$ and $12$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 \cdot - 17 + 25 | \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |) + 0$

Step 8.2.5.4

Evaluate $| \begin{array}{c} 1 & 1 \\ 1 & 3 \end{array} |$ .

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Step 8.2.5.4.1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 \cdot - 17 + 25 (1 \cdot 3 - 1 \cdot 1)) + 0$

Step 8.2.5.4.2

Simplify the determinant.

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Step 8.2.5.4.2.1

Simplify each term.

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Step 8.2.5.4.2.1.1

Multiply $3$ by $1$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 \cdot - 17 + 25 (3 - 1 \cdot 1)) + 0$

Step 8.2.5.4.2.1.2

Multiply $- 1$ by $1$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 \cdot - 17 + 25 (3 - 1)) + 0$

Step 8.2.5.4.2.2

Subtract $1$ from $3$ .

$- 1 \cdot - 36 + 0 + 2 (0 + 3 \cdot - 17 + 25 \cdot 2) + 0$

Step 8.2.5.5

Simplify the determinant.

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Step 8.2.5.5.1

Simplify each term.

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Step 8.2.5.5.1.1

Multiply $3$ by $- 17$ .

$- 1 \cdot - 36 + 0 + 2 (0 - 51 + 25 \cdot 2) + 0$

Step 8.2.5.5.1.2

Multiply $25$ by $2$ .

$- 1 \cdot - 36 + 0 + 2 (0 - 51 + 50) + 0$

Step 8.2.5.5.2

Subtract $51$ from $0$ .

$- 1 \cdot - 36 + 0 + 2 (- 51 + 50) + 0$

Step 8.2.5.5.3

Add $- 51$ and $50$ .

$- 1 \cdot - 36 + 0 + 2 \cdot - 1 + 0$

Step 8.2.6

Simplify the determinant.

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Step 8.2.6.1

Simplify each term.

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Step 8.2.6.1.1

Multiply $- 1$ by $- 36$ .

$36 + 0 + 2 \cdot - 1 + 0$

Step 8.2.6.1.2

Multiply $2$ by $- 1$ .

$36 + 0 - 2 + 0$

Step 8.2.6.2

Add $36$ and $0$ .

$36 - 2 + 0$

Step 8.2.6.3

Subtract $2$ from $36$ .

$34 + 0$

Step 8.2.6.4

Add $34$ and $0$ .

$34$

$D_{z} = 34$

Step 8.3

Use the formula to solve for $z$ .

$z = \frac{D_{z}}{D}$

Step 8.4

Substitute $- 2$ for $D$ and $34$ for $D_{z}$ in the formula.

$z = \frac{34}{- 2}$

Step 8.5

Divide $34$ by $- 2$ .

$z = - 17$

Step 9

List the solution to the system of equations.

$w = 5$

$x = - 9$

$y = - 34$

$z = - 17$