You went to the State Fair and spent $20. If cotton candy costs $2 and a soda pop costs $1. Which equation represents the relation between the number of cotton candy (c) and soda pops (s) you can buy?

Our total cost for 20 at the state fair is:
Cost of Cotton Candy + Cost of Soda = 20

We know that price = cost * quantity, so we have:
2c + 1s = 20