Qisi reads a 180-page story book, and has already read 80 pages, and needs to finish reading the rest within 5 days. How many pages do he need to read on average every day?
奇思看一本180页的故事书，已经看了80页，剩下的要再5天内看完，平均每天要看多少页？
<gadget id="calculator">180 - 80</gadget>
<output>100</output>

<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<result>20</result>