Since this is an equation involving an absolute value, let 2x + 6 be positive first such that,
-3(2x + 6) = -12
2x + 6 = 4
2x = -2, x = -1
Then, let 2x + 6 be negative,
-3(-2x - 6) = -12
-2x - 6 = 4
-2x = 10 ; x = -5
Thus, the answer to this item is letter B.