There are two piles of coal. The ratio of the coal stored in the first pile to the second pile is 12:7. After being removed from the first pile (1/4), the second pile is 3.6 tons less than the first pile. How many tons of original coal?
有两堆煤，原来第一堆与第二堆存煤量的比是12：7，从第一堆运走(1/4)后，第二堆比第一堆少3.6吨，第一堆原有煤多少吨？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">12 * (3/4)</gadget>
<output>9</output>

<gadget id="calculator">9 - 7</gadget>
<output>2</output>

<gadget id="calculator">3.6 / 2</gadget>
<output>1.8</output>

<gadget id="calculator">1.8 * 12</gadget>
<output>21.6</output>

<result>21.6</result>