How do I answer this?

Question

Pizza Palace charges a fixed amount for a basic pizza plus an additional cost per topping. It costs $2.15 for each topping. A 3-topping pizza costs $13.25. Find an equation for the line relating cost, C, in dollars, and number of toppings, t.

Answer 1

Cost of base pizza = 13.25 - 2.15 *3 = 6.8

And pizza price go up for each topping added, so the equation for line is given by

C= 2.15t + 6.8