For a book, Xiaohua read all (2/5) on the first day and all (1/5) on the second day, how much of the book is left.
一本书，小华第一天看了全部的(2/5)，第二天看了全部的(1/5)，还剩下全书的多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">1 - (2/5) - (1/5)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>