Heres a problem for ya. I can manage when the (ax) does not have a power, but not sure in this case.
Find the coefficient of $\displaystyle x^3$ in $\displaystyle ( 3x^2 - 5/x ) ^3$
Interesting problem.
As a binomial expansion with a power of three, the coefficients of the terms will be 1, 3, 3, 1, and in this case, the second term is the one of interest: