Xiao Liang bought a pencil case, paid the salesperson 20 yuan, and got back 12.5 yuan. How much is this pencil case?
小亮买了一个铅笔盒，付给售货员20元钱，找回了12.5元，这个铅笔盒多少元钱？
<gadget id="calculator">20 - 12.5</gadget>
<output>7.5</output>

<result>7.5</result>