There is a book that Xiao Ming has already read (2/5), how much of the book is left.
有一本书，小明已经看了(2/5)，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 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>