Greetings From Brasil...
Be
G(X) = 3X - 3
H(X) = 2X - 3
(GoH)(X) = G(H(X))
So, just replace the X of G(X) by the function H(X)
G(H(X)) = 3 · H(X) - 3
G(H(X)) = 3 · (2X - 3) - 3
G(H(X)) = (6X - 9) - 3
