A pile of coal has 65 tons, if (2/5) is used up, how many tons are left?
一堆煤有65吨，用去(2/5)，还剩多少吨．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">65 * (3/5)</gadget>
<output>39</output>

<result>39</result>