Anyone wanna help teach me how to do any of this or just give me the answers if you don't wanna teach me

just replace the value in the appropriate equation:
a) says f(-2)
so use the f equation above it and replace x with -2
f(x) = 3x-5 becomes f(-2) = 3x-5 =
3(-2)-5 = -6-5 = -11
for b use the equation for h and replace x with -5
so x^2 - 6 = -5^2 - 6 = -31
for c use the equation for g and replace x with (a+b)
-7x+3 =
-7(a+b)+3 = -7a-7b+3