= (25p^2 q^-7) / r^6 ((r^2 q^3) / (5p))
= (25 p^2 q^-7 r^2 q^3) / (r^6 5 p)
= (125 p q^-4 r^2) / (5 r^6)
= (25 p q^-4 r^2) / r^6
= 25p q^-4 r^-4