Liu Ye reads an extra-curricular book. He reads (1/4) on the first day and (1/5) the next day, so how much of this book has he not read?
刘烨看一本课外书，第一天看了(1/4)，第二天看了(1/5)，那么这本书还有多少没看？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

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