Jack bought 3 books a month at $20 each.  He sells them back at the end of the year for $500.  How much money did he lose?
He bought 3*20=$
<gadget id="calculator">3*20</gadget>
<output>60</output>
60 of books a month.
That means he bought 60*12=$
<gadget id="calculator">60*12</gadget>
<output>720</output>
720 of books a year.
So he lost 720-500=$
<gadget id="calculator">720-500</gadget>
<output>220</output>
220.

<result>220</result>