If (1/5) of a 10-meter-long iron wire is used up, then (1/5) meter is used up, how many meters are left?
10米长的铁丝，用去它的(1/5)后，又用去(1/5)米，还剩下多少米．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 * (1/5)</gadget>
<output>2</output>

<gadget id="calculator">10 - 2 - (1/5)</gadget>
<output>39/5 = around 7.8</output>

<result>39/5 = around 7.8</result>