A book has 100 pages, Xiaoxiao has already read 80 pages, and finished the remaining 5 days. How many pages do you read on average per day?
一本书100页，笑笑已经看了80页，剩下的5天内看完．平均每天看多少页？
<gadget id="calculator">100 - 80</gadget>
<output>20</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<result>4</result>