F(2x) = 8x-9 f(3x+1) = (x+5) (f+g)(x) = ...

f (2x) = 8x -9
f (2x) = 4(2x) -9
f (x) = 4x -9
g(3x+1) = x +5
g (3x+1) = 1/3(3x+1) + 4 2/3
g (x) = 1/3x + 4 2/3
(f + g)(x) = 4x -9 + 1/3x + 4 2/3
= 4 1/3 x - 4 1/3