Is square root of 400 not a real number ?

Which problem could be  solved  by evaluating the expression  7×(−3)7×-3?

Which will form a composite function?

Arestaurant offers delivery for their pizzas. the total cost the customer pays is the price of the pizzas, plus a delivery fee. one customer pays $23 to have 2 pizzas delivered. another customer pays $59 for 6 pizzas. how many pizzas are delivered to a customer who pays $86?