Given:
Number of choices offered, n = 15
Number of toppings (sample), r = 4
Let's find the number of possible 4-topping pizzas possible.
To solve this exercise, we are to use combination.
Combination involves the arrangement of objects without any repitition of orders of arrangement.
Apply the formula:
Thus, we have:
Solving further:
Therefore, there are 1365 possible 4-topping pizzas.
ANSWER:
1365