Wang Hua buys 5 pens of the same type, pays the salesperson 20 yuan, and gets back 2.5 yuan. How much is each pen?
王华买5支同样的笔，付给售货员20元，找回2.5元，每支笔多少元？
<gadget id="calculator">20 - 2.5</gadget>
<output>17.5</output>

<gadget id="calculator">17.5 / 5</gadget>
<output>3.5</output>

<result>3.5</result>