You saw a shirt for $97. You didn’t have the cash, so you borrowed $50 from your mum and $50 from your dad = $100. You bought the shirt, and had $3 change. You gave your dad $1 and your mum $1 and kept the other $1 for yourself. Now you owe your mum $49 and your dad $49. 49+49 = 98 + your $1 = 99. Where is the missing $1?