The 7th grade students at palm coast middle school made some apple pies for a bake sale. the school cafeteria also donated 9 pies toward the effort. all the pies at the sale were cut into 8 pieces. if at least 224 pieces of pie were sold in all, how many pies did the students bake?

So you know the school donated 9 pies, so you want to know how many pieces are in 9 pies. (remember 8 pieces per 1 pie) 
9 x 8 = 72

Next you subtract the amount you got to total amount.(224)

So 224 - 72 is 152.

152 is how many pieces of pie were sold by students.

To configure this number back to amount of pie, you basically need to divide by 8(number of pieces in 1 pie).

152 divided by 8 is 19. So 19 pies were sold by students.

Hope this helped!