$\"\"$

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The given equation is $\"\"$

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$\"\"$ (Using distributive property: a (b+c) =ab+ac)

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$\"\"$ (Multiply: 12(3) =36; 2(5) =10)

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$\"\"$ (Using commutative property: a+b=b+a)

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

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$\"\"$ (Add r to each side)

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$\"\"$ (Using commutative property: a+b=b+a)

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$\"\"$ (Add: $\"\"$ )

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$\"\"$ (Subtract 36 from each side)

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

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$\"\"$ (Divide each side by 13)

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$\"\"$ (Cancel common terms)

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$\"\"$

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$\"\"$ (Cancel common terms)

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$\"\"$

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Verify:

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To check the solution substitute $\"\"$ in original equation.

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Add: $\"\"$ )

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

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$\"\"$ (Add: $\"\"$ )

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Compare the values, the equation is true. The solution is $\"\"$ .

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$\"\"$

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The value of r is $\"\"$ .

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