$\"\"$

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The equations are

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$\"\"$ Equation (1)

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$\"\"$ Equation (2)

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$\"\"$ Equation (3) $\"\"$

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The second equation is $\"\"$

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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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Substitute 3 for a in equation (1).

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$\"\"$

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

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$\"\"$ (Subtract 6 from each side).

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$\"\"$ (Subtract)

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$\"\"$

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Substitute $\"\"$ and $\"\"$ in equation (3).

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$\"\"$

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

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$\"\"$ (Add 1 to each side).

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$\"\"$ (Simplify)

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$\"\"$

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The solution is $\"\"$ .