John buys 8 packs of cookies at the grocery store. The cookies are on sale for 50 cents off per pack. He spends $20. Which equation can be used to find the original cost of a box of cookies, c?
8 (c + 0.50) = 20
8(c - 0.50) = 20
The correct equation is:
8 (c - 0.50) = 20