Could someone please explain how to find the composition of a function.

Using this one as an example.

f(x)=x^3 and g(x)=3square root x. find g(f(x))

Plz hurry finals a paper cup in the shape of an inverted cone is 8 inches tall and has a radius of 1.5 inches. how much water can the cup hold? use 3.14 for pi. round the answer to the nearest tenth. a) 12.6 cubic in. b) 18.8 cubic in. c) 37.7 cubic in. d) 56.5 cubic in.