You see some $97 shoes, but don't have any money, so you borrow $50 from your mom & $50 from your dad = $100. You buy the shoes and have $3 change, so give your mom $1, give your dad $1 & keep $1 for yourself. You now owe your mom $49 & your dad $49. So.. $49 + $49 = $98 & your $1 = $99. So where is the missing $1?