Chapter 7 - Exponents and Exponential Functions - 7-2 Multiplying Powers With the Same Base - Practice and Problem-Solving Exercises - Page 429: 19

-$\frac{240m^{3}}{r}$. OR -240$m^{3}$$r^{-1}$

-$m^{2}\times4r^{3}\times12r^{-4}\times5m$ = -$m^{2}\times4r^{3}\times\frac{12}{r^{4}}\times 5m$ = $\frac{(-1\times4\times12\times5)(m^{2+1})}{r^{4-3}}$ =$\frac{-240m^{3}}{r} = -240$m^{3}r^{-1}$