The solution of {2x by = 123x + ay = 5 is {x = 3, y = 2, find 3a-2b

The solution of {2x by = 123x + ay = 5 is {x = 3, y = 2, find 3a-2b

Reference answer: substitute x = 3, y = 2 into {2x by = 123x + ay = 5
6-2b=12,.b=-3
9+2a=5.a=-2
So 3a-2b = - 6 + 6 = 0