Answer:
11x+4
Step-by-step explanation:
To do this, we can substitute 3x+10x for f(x) and 2x-4 for g(x), and we get 13x-(2x-4). By distributing the negative to 2x-4, we just swap the signs, and get 13x-2x+4, which equals 11x+4
Also, is there supposed to be an exponent on the first f(x)? I'm not sure because I haven't seen the real problem.
(Otherwise it would just be f=13x.) Maybe try being a little more clear when asking a question :)
Please let me know if you need more help or explanation on another problem!