@Amar123 Total there is 13 slice we can eat which consist of 5 types of pizza .
Each slice is from any of the 5 type of pizza.
So it is given we have to include all types of pizza at least one .
So from 13 slice 5 slices are fixed as 5 types of pizza .
there are 8 slices possible which can be fill be any of 5 types of pizza.
now apply star and bar and solve.
Yeah understood !! Thanks @Kabir5454