80% of a highway has been repaired, and how much remains to be repaired.
一条公路，已修80%，还剩多少没修．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

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

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