The cooking club made some pies to sell at a basketball game to raise money for the new math book. the cafeteria contributed three pies to the sale. each pie was then cut into seven pieces and sold. there were a total of 91 pieces to sell. how many pies did the club make?

Well, if the cafeteria contributed 3 pies and they were cut into 7 pieces, there would be 21 pieces of pie.
If you subtract that from 91 pieces they sold it would equal to 70 pieces. You then divide that into 7 pieces (to make a whole) and you get 10.
So the cooking club made 10 pies