-3
1) Let's work with this composite functions regarding f(x)= 3x +5, and g(x)=5-x
f(g(x)) In this case let's plug into the x variable of f(x) the function g(x)
a) f(g(x)) = 3(5-x) +5 = 15-3x+5=-3x+20
b) g(f(x))= 5-(3x+5) =5 -3x-5 = -3x
c) In this case, we can pick the composite function f(g(x)) and then plug into that x=0
f(g(x))=-3x +20
f(g(0))=-3(0)+20
f(g(0))= 20
2) Hence, the answer is:
f(g(x)) = 3(5-x) +5 = -3x+20
g(f(x))=-3x
f(g(0))=20
