text: what is f(x)=2x+3f(6)? i dont even understand this problem i am going to shot for 15  as the answer. don't let thte f(x) scare you all it means is x they just get fancy. but if you look at the problem f(x)=f(6) so what that means is x=6 so just plug in the 6 for the x and you should get the answer.