To build a (4/5) kilometer ditch, the full length (3/4) has been repaired, how many kilometers are left to be repaired?
修一条(4/5)千米的水沟，已经修了全长的(3/4)，还剩多少千米没有修？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(4/5) * (1/4)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>