If the number of pages that have been read in a book is the number of remaining pages (2/5), then how much do the remaining pages of the book account for in the total number of pages in the book?
一本书已看过的页数是剩下页数的(2/5)，则该书剩下的页数占这本书总页数的多少．
<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<result>5/7 = around 0.714286</result>