book, read 20% of the whole book on the first day, read 25% of the whole book on the second day, read 10 pages more on the second day than on the first day, how many pages does this book have?
一本书，第一天看全书的20%，第二天看了全书的25%，第二天比第一天多看10页，这本书共有多少页？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">10 / (1/20)</gadget>
<output>200</output>

<result>200</result>