Okay, let's see. So just to make sure I have the problem clear... your two equations are 2^{x+y} = 6^{y} and 3^{x} = 6 \cdot 2^{y}. Fun looking problem, really. Well, let's see... if you multiply both sides of the second equation by 2^x, you get this:
6^{x} = 6 \cdot 2^{x+y}
Then if we...