Answer:
-3·m^12·n^6
Explanation:
We assume you intend ...
(-24·m^5·n^4)/(8·m^-7·n^-2)
= (-24/8)·m^(5-(-7))·n^(4-(-2))
= -3·m^12·n^6
_____
If you really intend what you have written, then it simplifies to ...
(-24·m^5·n^4/8)·m^-7·n^-2 . . . . . note that all factors involving m and n are in the numerator
= (-24/8)·m^(5-7)·n^(4-2) = -3n^2/m^2