if you can buy 2 pair of pants and 1 shirt for 79.85$ before tax is added and 1 pair of pants and 2 shirts for 69.85$ before tax is added , how much does a shirt cost ?

2p + 1s = 7985

1p + 2s = 6985

first x 2 --->

4p + 2s = 15970
1p + 2s = 6985

subtract them

3p = 8985
p = 2995

carry on from there