Pre-Algebra Examples

$\frac{7^{9}}{7^{n}} = 7^{3}$

Step 1

Move $7^{n}$ to the numerator using the negative exponent rule $\frac{1}{b^{- n}} = b^{n}$ .

$7^{9} \cdot 7^{- n} = 7^{3}$

Step 2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$7^{9 - n} = 7^{3}$

Step 3

Since the bases are the same, then two expressions are only equal if the exponents are also equal.

$9 - n = 3$

Step 4

Solve for $n$ .

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Step 4.1

Move all terms not containing $n$ to the right side of the equation.

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Step 4.1.1

Subtract $9$ from both sides of the equation.

$- n = 3 - 9$

Step 4.1.2

Subtract $9$ from $3$ .

$- n = - 6$

Step 4.2

Divide each term in $- n = - 6$ by $- 1$ and simplify.

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Step 4.2.1

Divide each term in $- n = - 6$ by $- 1$ .

$\frac{- n}{- 1} = \frac{- 6}{- 1}$

Step 4.2.2

Simplify the left side.

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Step 4.2.2.1

Dividing two negative values results in a positive value.

$\frac{n}{1} = \frac{- 6}{- 1}$

Step 4.2.2.2

Divide $n$ by $1$ .

$n = \frac{- 6}{- 1}$

Step 4.2.3

Simplify the right side.

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Step 4.2.3.1

Divide $- 6$ by $- 1$ .

$n = 6$