see that ΔABC~ΔFGH?
that means the triangles are congruent, basically take the easy way and realize that C=H, A=F, and B=G.
y=6
now, for x, we use a²+b²=c²
so, 5²+x²=6²
(25)+x²=(36)
now we know that we need x² to equal 11
but, the square root of 11 isn't a whole number, so just put it in its radical form
x = [tex] \sqrt{11} [/tex]