Xiao Ming reads a 40-page story book and has already read 25 pages. How much of the book is left unread?
小明看一本40页的故事书，已经看了25页，还剩下这本书的几分之几没有看？
<gadget id="calculator">40 - 25</gadget>
<output>15</output>

<gadget id="calculator">15 / 40</gadget>
<output>3/8 = around 0.375</output>

<result>3/8 = around 0.375</result>