Your in a jewlers and you see a watch you like it costs £97.
You dont have the money to buy it so you borrow £50 off your mother and £50 pounds off your father which make £100
You buy the watch and get £3 change
You then give your mother £1 and your father £1 back and keep £1 for yourself
You now owe your mother £49 and your father £49
£49+£49=£98+ the £1 that you kept =£99 but where is the mising £1