Solve for a
a=-20
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2a-28-4a=12
Use the distributive property to multiply -4 by 7+a.
-2a-28=12
Combine 2a and -4a to get -2a.
-2a=12+28
Add 28 to both sides.
-2a=40
Add 12 and 28 to get 40.
a=\frac{40}{-2}
Divide both sides by -2.
a=-20
Divide 40 by -2 to get -20.
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