There are two piles of coal with a total of 76.5 tons. After the first pile is removed (3/4) and the second pile is removed (4/5), the remaining coal in the two piles is exactly the same. How many tons is the original difference between the two piles of coal?
有两堆煤共76.5吨，第一堆运走(3/4)，第二堆运走(4/5)后，两堆所余的煤正好相等，两堆煤原来相差多少吨．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">76.5 * (4/5)</gadget>
<output>61.2</output>

<gadget id="calculator">76.5 - 61.2</gadget>
<output>15.3</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4) - (4/5)</gadget>
<output>-11/20 = around -0.55</output>

<gadget id="calculator">1 + (-11/20)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">15.3 / (9/20)</gadget>
<output>34</output>

<gadget id="calculator">76.5 - 34 - 34</gadget>
<output>8.5</output>

<result>8.5</result>