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

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The equation is $\"\"$ .

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According to subtraction property of equality: if a = b, then a - c = b - c.

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$\"\"$ (Subtract 7 from each side)

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$\"\"$ (Commutative property: a + b = b + a)

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$\"\"$ (Additive inverse property: 7 - 7 = 0)

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

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$\"\"$

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

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$\"\"$ (Divide each side by 3)

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$\"\"$ (Cancel common terms)

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$\"\"$

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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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$\"\"$ (Cancel common terms)

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

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$\"\"$

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The value of $\"\"$ .