Xiao Ming borrowed a book. He originally planned to read 20 pages a day and finished it in 15 days. Now he has to return it 3 days in advance. How many more pages must he read every day?
小明借了一本书，原计划每天看20页，15天看完，现在要提前3天归还，每天必须多看多少页？
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">300 / 12</gadget>
<output>25</output>

<gadget id="calculator">25 - 20</gadget>
<output>5</output>

<result>5</result>