Stacey used her 20% discount card to buy 7 cans of tomatoes and 15 cans of mushrooms for $10.64. The next day Brian spent $ 7.21 on 17 cans of tomatoes and 5 cans of mushrooms in a "30% off" sale. Find the undiscounted pre- sale price of each type of can.

Answer 1

let's use T for tomato and M for mushroom,Stacey:$10.64 is 80% of the original price of 7T and 15M so 20% discount will equal to 2.66 and the original price will be 13.3.
Brian:7.21 is 70% of the original price of 17T and 5M so 30% will equal to 3.09 and the original price will be 10.3.
Stacey:7T+15M=13.3
Brian:17T+5M=10.3
now multiply Brian by 5 will get
7T+15M=13.3
51T+15M=30.9
now subtract it will get
44T=17.6 and T=$.40 and M=$.70