My solution

Fact 1) The L.H.S. must be a multiple of 3

Fact 2) If 0<y\leq{3}, then the R.H.S. is positive, but the L.H.S. is -ive, hence y>3

Fact 3) If y>22, a similar situation occurs, so 3<y<22

Fact 4) y cannot be a multiple of 3, as the L.H.S. would not be multiple of 3

Fact 5) I have stopped determining constraints and begun to guess the answer

Upon guessing, y=7 and x=2

So the value of follows