Help with these would be nice =)

Solve the simultaneous equations:

2^x - 3^y = 7

2^x-1 + 3^y+1 = 35

And another question:

If 2,1 is a solution to the equations: x^2 + xy + ay = b, and 2ax + 3y = b, find the other solution.

I did:

4 + 2 + a = b --(1)

4a + 3 = b -- (2)

4a + 3 = 6 + a

a = 0.6

b = 6.6

Then I substituted it into the original equations to get:

x^2 + xy + 0.6y = 6.6 -- (3)

1.2x + 3y = 6.6 --(4)

But I can't get anywhere with it...