Answer
Find out the how many pizzas are delivered to a customer who pays $80 .
To prove
As given
A restaurant offers delivery for their pizzas.
The total cost is a delivery fee added to the price of the pizzas.
One customer pay $25 to have 2 pizzas delivered.


Another customer pays $58 for 5 pizzas.


Thus by using the slope formula

Putting the value in the formula


Simplify the above

This represented one pizza cost is $11.
Thus 2 pizza cost = $11 × 2
= $22
Thus
Delivery price = Total cost of 2 pizza including delivery fee - Cost of 2 pizza
= $25 - $22
= $3
Thus 5 pizza cost = $11 × 5
= $55
Thus
Delivery price = Total cost of 5 pizza including delivery fee - Cost of 5 pizza
= $58 - $55
= $3
Therefore the delivery charge is $3.
Now calculate the number of pizza for the customer who pays $80.
Cost of the pizza = Total cost of the pizza including delivery charges - Delivery charges
= $80 - $3
= $ 77
Let us assume that the number of pizza for the customer who pays $80 = x
Cost of one pizza = $11
Than the equation becomes
11 × x = 77

x = 7
Therefore the number of pizza are 7 delivered to a customer who pays $80 .