A pile of coal weighs 2 tons, all (2/5) is used on the first day, and (2/5) tons is used on the second day, how many tons are left?
一堆煤重2吨，第一天用去全部的(2/5)，第二天用去(2/5)吨，还剩多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 * (2/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2 - (4/5) - (2/5)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>