Substitution method:

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$\"\"$ ---------->( 1 )

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$\"\"$ ---------->( 2 )

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Substitute the value of $\"\"$ in (2).

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$\"\"$

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$\"\"$ \ \

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$\"\"$

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Add 28 to each side. \ \

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$\"\"$

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$\"\"$

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Divide each side by 3.

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$\"\"$

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$\"\"$

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Substitute the value $\"\"$ in (1).

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$\"\"$

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$\"\"$

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$\"\"$ .

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Solution $\"\"$ and $\"\"$ .