For a book, I read (1/4) of the whole book on the first day, but I read 7 pages less than (2/5) of the whole book on the second day, and there are still 35 pages left unread. How many pages is this book?
一本书，第一天读了全书的(1/4)，第二天读的比全书的(2/5)少7页，还有35页没有读．这本书共多少页？
<gadget id="calculator">35 - 7</gadget>
<output>28</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">28 / (7/20)</gadget>
<output>80</output>

<result>80</result>