This is a composite. Another way to write them is f(g(x)). Take the function g(x) and stick it in for x in f(x). Like this:
![f(g(x))= ((3x+1)-1)/(3)](https://img.qammunity.org/2019/formulas/mathematics/high-school/bnv6qzlmyy8q3fgbmtnljsxdvqw69l6wm9.png)
. But we aren't done cuz there's some simplifying there to do.
![f(g(x))= (3x)/(3)](https://img.qammunity.org/2019/formulas/mathematics/high-school/rzcq72maoqj0rr5x6944gz4uwcv3ulgx39.png)
and canceling out the 3's we get just a simple x as our answer. The choice is the last one above as your answer.