You can
put this solution on YOUR website!
Hi, You are absolutely correct
4^x (2^y)=16
(2^2x)(2^y) = 2^4
In general, 
2^(2x+y) = 2^4 both sides of equation with the same base
Exponents are also equal
8^x= 2^(y/2)
2^3x = 2^(y/2)
3x = y/2
6x = y
2x + y = 4
2x + 6x = 4 Substituting 6x for y
8x = 4
x = 1/2 y = 3 (6*(1/2)