Build a canal of x meters long, (2/5) has been repaired, how many meters are left.
修一条长x米的水渠，已经修好了(2/5)，还剩多少米．
<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>