A pile of coal has been used up (3/5), and there are still 12 tons left. How many tons were there in this pile of coal?
一堆煤用去(3/5)，还剩下12吨，这堆煤原来有多少吨？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

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

<result>20</result>