A pile of coal, 40% of the first time was used, and 1/3 of the original total amount was used for the second time, leaving 12 tons left. How many tons is this pile of coal?
一堆煤，第一次用去40%，第二次用去原来总量的(1/3)，还剩余12吨．这堆煤共有多少吨？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (2/5) - (1/3)</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">12 / (4/15)</gadget>
<output>45</output>

<result>45</result>