Li Li read a story book, read the whole book (5/42) on the first day, read 40 pages more than the first day on the second day, and read the whole book (1/7) on the third day. There is still half of the book that has not been read. How many pages are there in this book?
李丽读一本故事书，第一天读了全书的(5/42)，第二天比第一天多读40页，第三天读了全书的(1/7)，这时，正好还有一半书没有读，这本书共多少页？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">5 / 42</gadget>
<output>5/42 = around 0.119048</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/2) - (5/42) - (1/7) - (5/42)</gadget>
<output>5/42 = around 0.119048</output>

<gadget id="calculator">40 / (5/42)</gadget>
<output>336</output>

<result>336</result>