Solve for a
a=7
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3a-6=15
Swap sides so that all variable terms are on the left hand side.
3a=15+6
Add 6 to both sides.
3a=21
Add 15 and 6 to get 21.
a=\frac{21}{3}
Divide both sides by 3.
a=7
Divide 21 by 3 to get 7.
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