Answer :

AL2006
                             5 pizza / 6 student  =  'Z' pizza / 1 student

Cross-multiply the proportion:       

                             5 pizza-student  =  6 Z  pizza-student

Divide each side of the equation by 6 pizza-student :        

                             5/6  =  Z

Each student gets 5/6 of 1 pizza.

It's not so complicated.  Cut each pizza into 6 slices,
and each student gets 5 slices.

That's the same as  (83 and 1/3) percent of a pizza.