The school brought a pile of coal, used up (2/5), and there are 20 tons left, how many tons of this pile of coal were used?
学校运来一堆煤，用去了(2/5)，还剩下20吨，这堆煤用了多少吨？
<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">20 / (3/5)</gadget>
<output>100/3 = around 33.333333</output>

<gadget id="calculator">(100/3) - 20</gadget>
<output>40/3 = around 13.333333</output>

<result>40/3 = around 13.333333</result>