Answer: a = -6
Explanation
First, do the distributive property:
a -2(a - 3) = 12
a - 2a + 6 = 12
Next, add like terms:
a - 2a + 6 = 12
-1a + 6 = 12
Now subtract 6 from both sides:
-1a + 6 - 6 = 12 - 6
-1a = 6
Divide both side by -1:
-1a/-1 = 6/-1
a = -6
Check your answer:
(-6) - 2[(-6) - 3] = 12
(-6) - 2(-9) = 12
(-6) - (-18) = 12
-6 + 18 = 12
12 = 12