Question

3 regular pizzas and 2 small pizzas cost $31.
9 regular pizzas and 8 small pizzas cost $103.
What's the cost of 1 regular pizza?
What's the cost of 1 small pizza?

Answer 1

first of all, lets set up the equation

3x + 2y = 31

9x + 8y = 103

+--------------------

now make them equal

12x + 8y = 124

9x + 8y = 103

+----------------------

x=7

y=5