First, let's substitute a=4 into the first equation:

9(4) + 3(4-5)
36 + 3(-1)
36 - 3
33

Now, let's substitute b=6 into the second equation:

52 + 4(11+6)
52 + 4(17)
52 + 68
120

Therefore, the solutions are:

a = 33
b = 120