Happy Joes has a deal this week on their specialty pizzas. You can get any specialty pizza you'd like for the same price, tax free for schools - all you have to do is pay for delivery. This math department ordered 4
pizzas and paid $82.75. The English department paid $138.25 for 7 pizzas.

Define the variables:

x:
y:

Create an equation:


How much was the delivery charge?