$\"\"$

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The proportion is $\"\"$ .

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Multiply each side by $\"\"$ .

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$\"\"$

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Cancel common terms.

\

$\"\"$ . $\"\"$

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Apply cross products property: If $\"\"$ where $\"\"$ then $\"\"$ .

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$\"\"$

\

$\"\"$

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Subtract d from each side.

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$\"\"$

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$\"\"$

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$\"\"$

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Add 39 to each side.

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$\"\"$

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$\"\"$

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$\"\"$

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Divide each side by 2.

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$\"\"$

\

Cancel common terms.

\

$\"\"$ . $\"\"$

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To check the solution, substitute the value of $\"\"$ in the proportion $\"\"$ .

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$\"\"$

\

$\"\"$

\

$\"\"$

\

Cancel common terms.

\

$\"\"$ . $\"\"$

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The value of $\"\"$ .