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

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The expression is $\"\"$ .

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

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

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According to Addition property of equality:Add $\"\"$ to each side.

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$\"\"$

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$\"\"$ (Apply commutative property of addition: $\"\"$ )

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

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$\"\"$ (Add: $\"\"$ ) $\"\"$

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According to subtraction property of equality:Subtract 18 from each side.

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$\"\"$

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

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

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$\"\"$ (Multiply each side by negative one)

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$\"\"$ (Product of two same signs is positive) $\"\"$

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According to division property of equality:If $\"\"$ then $\"\"$ .

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

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$\"\"$ (Cancel common terms) $\"\"$

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Check:

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To check the solution, substitute $\"\"$ in original equation.

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$\"\"$

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

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$\"\"$ (Subtract: 18 $\"\"$ 15 = 3)

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

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Compare the values, the equation is true. $\"\"$

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The value of $\"\"$ .