A road is 500 meters long, 20% of it has been repaired, how many meters are left to be repaired?
一条路长500米，修了20%，还剩多少米没有修．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">500 * (4/5)</gadget>
<output>400</output>

<result>400</result>