If you have read 75% of a book and have 40 pages more than you have not read, how many pages does this book have?
一本书已经读了75%，比没读的多40页，这本书有多少页？
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(3/4) - (1/4)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">40 / (1/2)</gadget>
<output>80</output>

<result>80</result>