Xinhua Bookstore has 750 story books, and after 5 days of selling, there are still 250 books left. How many books are sold per day on average?
新华书店有750本故事书，卖出5天后还剩250本，平均每天卖出多少本？
<gadget id="calculator">750 - 250</gadget>
<output>500</output>

<gadget id="calculator">500 / 5</gadget>
<output>100</output>

<result>100</result>