Awesome, thanks for posting an example.
So in this problem, we want to replace the x in f(x) with
h(x). That would give us f(12/x). So in the function for f(x), where there is an
x, we replace it with (12/x).
So, f(h(x)) becomes f(12/x) = (12/x)^2 + 7 = (144/x^2) + 7.
I hope that makes sense.