A piece of iron wire is 15 meters long, after subtracting the number of meters, there is still (1/5) of the full length.
一根铁丝长15米，减去多少米后，还剩下全长的(1/5)．
<gadget id="calculator">1 / 5</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">15 * (4/5)</gadget>
<output>12</output>

<result>12</result>