Choose the equivalent system of linear equations that will produce the same solution as the one given below.
6x + 2y = -6
3x - 4y = -18

A: 12x + 4y = -12
15x = -30

B: 8x + 4y = -4
14x = -10

C: 6x - 8y = -36
-6y = -42

D: 6x - y = -15
3y = 9