A florist has roses carnations lilies and snapdragons in sto

A florist has roses, carnations, lilies, and snapdragons in stock. How many different bouquets of one dozen flowers can be made?

The florist has 4 different types of flowers. So finally the question is reduced to x+y+z+a = 12 where x,y,z,a denotes the number of each of roses and we know all of them must be greater than or equal to 0. The answer for a questions of this sort is 16C4.