Xiaojia's mother gave the salesperson 50 yuan, bought 3 fountain pens, and got back 29 yuan. How much is each fountain pen?
小佳的妈妈给了营业员50元，买了3枝水笔，找回29元，每枝水笔多少元钱？
<gadget id="calculator">50 - 29</gadget>
<output>21</output>

<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<result>7</result>