A piece of iron wire is 2 meters long and 80 centimeters are used up ((())/(())). How much is left.
一根铁丝长2米，用去80厘米，用去((())/(()))．还剩下多少．
<gadget id="calculator">2 * 100</gadget>
<output>200</output>

<gadget id="calculator">80 / 200</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>