Y=a(x-3)^2-1, what is the value of a

How are algebraic expressions evaluated using substitution?

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?

What is solution for the following system of equations, 2x+8y=4 and x=-3y+5 1) x=14 y=-3 2) x=2 y=-3 3) x=-3 y=-3 4)x=12 y=5