1. (f o g)(x) = f (g(x)) so to find an expression for (f o g)(x) you replace every occurence of x in the expression for f(x) by 2x - x2.
(g o f)(x) = g( f (x)) so to find an expression for (g o f)(x) you replace every occurence of x in the expression for g(x) by x3.