$\"\"$

The equations are

$\"\"$ Equation (1)

$\"\"$ Equation (2)

$\"\"$

Multiply equation (1) by 3.

$\"\"$ Equation (3)

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Substitute $\"\"$ in equation (1).

$\"\"$

Product of two different sings is negative.

$\"\"$

Apply addition property of equality: if a = b, then $\"\"$ .

Add 3 to each side.

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The solution is $\"\"$ .