Wang Xiaoyan's mother took 100 yuan to buy a 5-yuan pen, and got back 25 yuan. How many pens did she buy?
王小艳的妈妈拿100元买5元一枝的钢笔，找回了25元，她买了多少枝这样的钢笔．
<gadget id="calculator">100 - 25</gadget>
<output>75</output>

<gadget id="calculator">75 / 5</gadget>
<output>15</output>

<result>15</result>