Let's start with the most simple thing: we know that anything to the power of 0 is 1, so we change that. This gives us:
r^-1(s^-1) /r^-3(s)(q)(s)
from here, we can see that r^-1 is 1/r, same with the s^-1, and r^-3 is 1/r^3. So, plug that in:
1/r(1/s)/(1/r^3)(s)(q)(s)
(1/rs)/(s^2*q/r^3)
Finaly, we divide.
You should get r^2/qs^3
:)