Read a book, read (1/5) in the morning and (1/4) in the afternoon, how much of this book is left
读一本书，上午读了(1/5)，下午读了(1/4)，还剩这本书的多少
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/5) - (1/4)</gadget>
<output>11/20 = around 0.55</output>

<result>11/20 = around 0.55</result>