Xiaohong buys a pencil case, pays the salesperson 20 yuan, and gets back 13.8 yuan. How much is this pencil case?
小红买一个文具盒，付给营业员20元，找回13.8元，这个文具盒多少元？
<gadget id="calculator">20 - 13.8</gadget>
<output>6.2</output>

<result>6.2</result>