You owe your parents 10 dollars. If you give each parent a dollar, you now owe your parents 8 dollars. 8 plus 1 is 9, that's true, but 9 dollars is not how much you owe your parents. Recall that you owe your parents 8 dollars. Use the dollar that you kept from earlier to help pay your debt to them. 8 minus 1 is 7, and 7 dollars is how much your candy cost you. You could return the candy and get 7 dollars to pay off your debt, or you could just wait until your parents forget about it.