In order to evaluate any composite function, you need to first put the value in for the inside function. In this case f(x) is on the inside along with the number 3. So, we input 3 in for x in f(x).
f(x) = 2x + 1
f(3) = 2(3) + 1
f(3) = 6 + 1
f(3) = 7
Now that we have the value of f(3), we can stick the answer in for the outside function, which is g(x).
