A storybook is 12.5 yuan, a pen is 6.7 yuan, and Honghong pays the salesperson 20 yuan. How much should I get back?
一本故事书12.5元，一支钢笔6.7元，红红付给营业员20元，应找回多少钱？
<gadget id="calculator">20 - 12.5 - 6.7</gadget>
<output>0.8</output>

<result>0.8</result>