question: James gets 10 new CDs.  Each CD cost $15.  He gets them for 40% off.  He decides he doesn't like 5 of them and sells them for 40. How much money was he out?
answer: He got a 15*.4=$<<15*.4=6>>6 discount on each CD
  That means each CD cost 15-6=$<<15-6=9>>9
  So he paid 10*9=$<<10*9=90>>90
  That means he was out 90-40=$<<90-40=50>>50
  #### 50