John decided to sell his PlayStation to buy a new computer.  The computer's cost was $700 and the accessories cost was $200.  The PlayStation was worth $400 but he sold it for 20% less than its value.  How much money came out of his pocket?
He loses 400*.2=$<T>multiply(400, 0.2)=80.0 on the PlayStation
So he sells it for 400-80=$<T>subtract(400, 80)=320
The computer cost 700+200=$<T>add(700, 200)=900
So he was 900-320=$<T>subtract(900, 320)=580 out of pocket
