Factor 36 and add them, make sure both are negatie
1+36=37, nope
2+18=20 nope
3+12=15,nope
4+9=13, nope
6+6=12, nope
the closest one is 20
I hope you meant adds to -20, because if you did, then answer is -2 and -18
if you did mean 36 and adds to -21, then the numbers are

and

, aprox -19.1168 and -1.8831
I'll do the first one to get you started
So we have g(f(x)) which means that we start with g(x) and replace the 'x' with 'f(x)' to get g(f(x))
g(x) = ( x - 4 )/2
g(f(x)) = ( f(x) - 4)/2 .... replace every x with f(x)
g(f(x)) = (2x+4-4)/2 .... replace f(x) on the right side with 2x+4
g(f(x)) = (2x+0)/2
g(f(x)) = (2x)/2
g(f(x)) = 1x/1
g(f(x)) = 1x
g(f(x)) = x
Let me know if you need help with the other one.