What is the measure of AC? I need a step by step explanation because it's not edge it's a worksheet​

Prices: box of cereal: $2.78 can of soup $0.80 yogurt cup $0.67 package of cheese $2.08 : aaron bought 3 boxes of cereal 7 yogurt cups 1 package of cheese and a number of cans of soup he paid with a $20.00 bill and recieved $0.09 in change how many cans of soup did he buy