\"\"\"\"

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\"\"

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 Given equation is \"\".

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Apply addition property of equality: Add 3y to each side.

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\"\"

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Rearrange the terms using commutative property of addition: a+b = b+a.

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\"\"

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

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

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\"\"

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Apply 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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\"\"

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

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\"\"                     (Divide each side by 3)

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\"\"                         (Cancel common terms)

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\"\"                       (Simplify)

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

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\"\".

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\"\"

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The option "C" is correct.