Question 6721
I assume that by the way you have written your question, both logs have base 'b'?!

In that case:
1) {{{ 3(log(b,m)-3log(b,n))}}}
2) {{{ 3(log(b,m)-log(b,n^3))}}}
3) 3(log(b)m/(n^3)
4) log(b)(m/n^3)^3  <---- your answer.

In answering these types of questions, it is crucial that you know your 3 laws of logs.
Law 1:
log(x) + log(y) = log(xy)

Law 2:
log(x) - log(y) = log(x/y)

Law 3:
nlog(x) = log(x^n)

When the base of a log is not written, it usually implies that the base is 10. These laws only apply when the logs have the same base.

Hope that helps.
Regards,
-Mike