Pizza is available with three kinds of cheese and four toppings. how many different ways can you order your pizza with one type of cheese and two toppings

You will choose 1 cheese 3 different ways because there are three types of cheeses.

You will choose your topings 6 different ways. 4!/(2!2!) = 4*3/2 = 6

Therefore you will be able to get 6 * 3 different pizzas = 18 pizza combinations.

To confirm the toppings, suppose they are (M)ushrooms (P)epperoni (O)nions and (B)acon

M P
M O
M B
P O
P B
O B

Total 6.The order doesn't matter here. M O is the same thing as OM