Answer: Hi, in this problem we know the next things.
A large pizza cost 18 dollars, and each topping you want cost 1.50 dollars extra. So if you want c toppings, then you must pay 1.50*c dollars for those, where c must be a positive integer.
then the total price would be the sum of the 18 dollars for the pizza and 1.50* dollars extra for the toppings:
Total price = $18 + $1.50*c