$\"\"$ $\"\"$

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According to Means-extremes Property of proportion: Cross products.

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$\"\"$

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$\"\"$ (Apply distributive proeperty: $\"\"$ )

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$\"\"$ (Multiply: $\"\"$ ) \ \ $\"\"$

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According to subtraction property of equality: if $\"\"$ than $\"\"$ .

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$\"\"$ (Subtract 10 from each side)

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$\"\"$ (Apply additive inverse proerpty: $\"\"$ )

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$\"\"$ (Apply additive identity proerpty: $\"\"$ )

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$\"\"$ (Subtract: $\"\"$ ) $\"\"$

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According to division property of equality: if $\"\"$ than $\"\"$ .

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$\"\"$ (Divide each side by 5)

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$\"\"$ (Cancel common terms)

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$\"\"$ (Divide: $\"\"$ ) $\"\"$

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The value of $\"\"$ .