How do you simplify #(x^-1y^-2)/z^-3#?
Technically, this is already simplified to some extent. There are no like-terms that can be combined.
However, if you would like to write this in terms of only positive powers, then:
Negative powers keep the same power, but can be rewritten as positive if placed in the opposite part of the fraction. So a negative power in the numerator is equivalent to a positive power in the denominator, and vice-versa.