Last week, Leon bought 8 pizzas and 13 cakes for a total of $134.
Today, Leon bought 28 pizzas and 4 cakes for a
total of $220.
Assuming neither item has changed in price,
what is the cost of a pizza in dollars?

P = pizza and c =cakes

Last week: 8p + 13c = 134
Today: 28p + 4c = 220

Let’s take the formula for today and subtract 28p from each side to isolate the 4c.

4c = 220 - 28p

Now divide each side by 4

c = (220 - 28p)/4
Simplify to c = 55 - 7p

Now go to the formula for last week, substitute the c for 55-7p

8p + 13(55 - 7p) = 134
8p + 715 - 91p = 134

Simplify to 715 - 83p = 134

Let’s add 83p to each side.

715 = 134 + 83p

Subtract 134 from each side

581 = 83p

Divide each side by 83

p = $7