A book has 60 pages in total, 39 pages have been read, and the rest of the book ((())/(())) has not been read.
一本书共有60页，已经看了39页，还剩下全书的((())/(()))没看．
<gadget id="calculator">60 - 39</gadget>
<output>21</output>

<gadget id="calculator">21 / 60</gadget>
<output>7/20 = around 0.35</output>

<result>7/20 = around 0.35</result>