Xiaohong paid 20 yuan and bought x exercise books, each of which was 1.25 yuan. How much should she get back?
小红付出20元，买了x本练习本，每本1.25元，应找回多少元．
<gadget id="calculator">20 - 1.25</gadget>
<output>18.75</output>

<result>18.75</result>