20% of a pile of coal is used up, and the rest is 12 tons more than what was used. How many tons is there in this pile of coal?
一堆煤用去20%，剩下的比用去的多12吨，这堆煤有多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">12 / (3/5)</gadget>
<output>20</output>

<result>20</result>