story book has been read (2/5), the number of pages that have not been read is the number of pages that have been read
一本故事书，已经看了(2/5)，没看的页数是已看页数的多少
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) / (2/5)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>