Question

Please help?

Answer 1

3A + 5B = -12
wA - 15B = 6

multiply the first equation by 3, and add it to the second equation:
3(3A + 5B) = 3(-12)

so:
9A + 15B = -36
+
wA - 15B = 6
gives
(9+w)A = -30

This has no solution when 9+w = 0, as that would give:
0A = -30 or 0 = -30.

so solve 9+w = 0 for w.