For each of the following, find f(g(x)), g(f(x)), f(g(2)).
f(x) = 2x, g(x) = x + 7
f(x) = x + 4, g(x) = 2x + 1
f(x) = x^2 + 2, g(x) = x + 3
f(x)=sqrtx, g(x) = x + 2