Xiaoli reads 50 pages of the book, she has already read 20 pages, and finished reading in the remaining 10 days, how many pages she reads on average per day.
小丽看50页书，已经看了20页，剩下的10天看完，平均每天看多少页．
<gadget id="calculator">50 - 20</gadget>
<output>30</output>

<gadget id="calculator">30 / 10</gadget>
<output>3</output>

<result>3</result>