what is the moment of inertia of a hollow sphere with mass 5 kg and radius .5m
I know the equation is 2/3mR^2
but I don't know how to include the units

5 seconds + Google = The answer to you question (or a pointer in the right direction anyway)

In general, with physics formulas, you plug the units right into the formulas. Say you're trying to find distance, and you have acceleration of 9.8m/s^2, and time of 4s:

d=1/2 a t^2
= 1/2 (9.8m/s^2)(4s)^2
= 1/2 (9.8m/s^2)(16s^2)
= 78.4m (the s^2 and 1/s^2 cancel out)

You can plug the units right into your formula as well, and get the correct units for moment of inertia out the other end.