Step-by-step explanation:
Step 1:
(3x + 12y) + (10x - 5y)
{Distributive property A(B+C)=AB+AC}
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Step 2:
(3x + 12y) + (-5y + 10x)
{Commutative property A+B = B+A}
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Step 3:
3x + (12y - 5y) + 10x
{Associative property A+(B+C)=(A+B)+C}
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Step 4:
3x + 10x + (12y - 5y)
{Commutative property A+B = B+A}
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Step 5:
13x + 7y
{Simplification}
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