Answer:
I am not sure what you mean when you write [x], but let suppose [x] acts like a black box.
Then, f(x) =[x], range of f is any number satisfies that black box. For i.e: all complex and real number.
Same conclusion for g(x) =x-[x]
f(g(x)) = [x-[x]]
g(f(x)) = [x] - [[x]]
Here, without any detail(about the black box [ ]), then f(g(x)) = g(f(x)) with all x.
