For a pile of coal, 5 tons more than the total (2/9) was removed for the first time, 2 tons less than the remaining (2/5) for the second time, and 20 tons were removed for the third time, It just happened to be shipped, so how many tons of this pile of coal are there?
一堆煤炭，第一次运走的比总数的(2/9)要多5吨，第二次运走的比余下的(2/5)还少2吨，第三次运走20吨，刚好运完，问原来这堆煤炭共多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">5 * (2/5)</gadget>
<output>2</output>

<gadget id="calculator">20 - 2 - 2</gadget>
<output>16</output>

<gadget id="calculator">5 + 16</gadget>
<output>21</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">(2/9) * (2/5)</gadget>
<output>4/45 = around 0.088889</output>

<gadget id="calculator">(4/45) - (2/9) - (2/5)</gadget>
<output>-8/15 = around -0.533333</output>

<gadget id="calculator">1 + (-8/15)</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">21 / (7/15)</gadget>
<output>45</output>

<result>45</result>