Answer:
A = 6, B = -15
Step-by-step explanation:
In order for there to be infinitely many solutions, the equations must be dependent. That is, one of them must be a multiple of the other. Here, the multiplier is apparently -1.
Comparing coefficients on the left, we see that the bottom equation has an x-coefficient that is the opposite of the one in the top equation. So, to make y-coefficients opposite, the top equation should read ...
4x -6y = 15 . . . . . A = 6
Carrying that through, the bottom equation should read ...
-4x +6y = -15 . . . . . B = -15
