that is actually easier thatn it looks
here is a tip
write that thing apart since they are all multiplication like this:
V=(1/3)pir^2 h
now just divide the whole equaiton by ((1/3)pir^2)
or if you don't like dividiing by fracitons, times both sides by 3/1 to clear fraction to get
3V=pir^2h
divide both sides by pir^2
(3v)/(pir^2)=h