Question 198608
sol:
(fof)(x)=f[f(x)]
  =f[x^3] (in our problem f(x)=x^3 substitute this value in the place of f(x))
again substitute x^3 in place of x in x^3
               f(x^3)=(x^3)^3
substitute x^3 in x
(fof)(x)=x^9    (i.e;(a^m)^n=a^mn)