Here are a few practice problems about compositions of functions to work in your journal.

(1)  If f(x) = 3x and h(x) = 4x, what is h(f(x))? How about f(h(x))?
(2) If f(x) = 3 and h(x) = 4x, what is h(f(x))? How about f(h(x))?
(3) If f(x) = x+5 and h(x) = x^2, what is f(h(x))?  How about h(f(x))? Here x^2 means "x squared", that is "x times x".
(4) If f(h(x)) = x + 2 and f(x) = x - 4, what is h(x)?