4(-3 + -2d) = 12
(-3 * 4 + -2d * 4) = 12
(-12 + -8d) = 12
-12 + -8d = 12
-12 + 12 + -8d = 12 + 12
-12 + 12 = 0
0 + -8d = 12 + 12
-8d = 12 + 12
12 + 12 = 24
-8d = 24
d = -3
8.5m questions
11.2m answers