Answer:
There are 342 different combinations.
Explanation:
Ok, Aileen is choosing toppings for a pizza.
She can choose two.
There are 19 options that can be chosen once.
The first thing we need to do, is find all the "selections".
Here we have two selections:
Topping number 1
Topping number 2.
Now we need to find the number of options for each one of these selections:
Topping number 1: Here we have 19 options.
Topping number 2: Here we have 18 options (because one was already taken in the previous selection)
The total number of combinations is equal to the product between the numbers of options.
C = 19*18 = 342
There are 342 different combinations.