I can't get the last question.....
A pizza company advertises that it has 15 toppings from which to choose (There are six vegetable toppings)
e) how many different 3 topping pizzas have at least one vegetable?
This is what i did:
6nCr3 = 20 15nCr3 = 455
455-19 = 436
The answer in the back of the book is:371