A book has a total of 300 pages, 20 pages have been read, and the remaining 7 days are finished, how many pages are read per day on average?
一本书共300页，已经看了20页，剩下的7天看完，平均每天看多少页？
<gadget id="calculator">300 - 20</gadget>
<output>280</output>

<gadget id="calculator">280 / 7</gadget>
<output>40</output>

<result>40</result>