Please help me find domain/ range and equation

Write the equations in logarithmic form 10^3=1,000

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?

Which of the following choices gives you a slope of 3?