The cost of a pizza is $10.50 for no toppings, $12 with 1 topping, $13.50 with 2 toppings, $15 with 3 toppings, etc. what is a recursive formula that represents the cost of a pizza with n toppings?

You can see the increase for topping is $1.5 from this you have the element: 1.5*n where "n" is the numbers of toppings, but you have to have the cost for the pizza without topping $10.50, so your formula is:

Cost pizza = 10.50 + 1.5n

You can prove this putting differents values for n also using n=0 and you will see the costs are the same those given.