Xiao Ming has been reading a 520-page storybook for 4 days, 25 pages a day, and plans to finish the rest in 12 days. How many pages can he read on average per day?
小明看一本520页的故事书，已看了4天，每天看25页，剩下的准备12天看完，平均每天看多少页才能看完？
<gadget id="calculator">25 * 4</gadget>
<output>100</output>

<gadget id="calculator">520 - 100</gadget>
<output>420</output>

<gadget id="calculator">420 / 12</gadget>
<output>35</output>

<result>35</result>