When Li Ming reads a book, he has already read 65% of the whole book, and the pages he has not read are 90 pages less than those he has read. How many pages does this book have?
李明看一本书，已经看了全书的65%，没看的比看了的少90页．这本书共几页？
<gadget id="calculator">65 / 100</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">1 - (13/20)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(13/20) - (7/20)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">90 / (3/10)</gadget>
<output>300</output>

<result>300</result>