A pile of coal, (1/5) was removed for the first time, and the rest (3/4) was removed for the second time, leaving 20 tons. How many tons did the pile of coal originally have?
一堆煤，第一次运走(1/5)，第二次运走余下的(3/4)，还剩下20吨，这堆煤原来有多少吨．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(4/5) * (3/4)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (1/5) - (3/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 / (1/5)</gadget>
<output>100</output>

<result>100</result>