A pile of coal is used up (1/3) for the first time, and the rest (2/3) is used up for the second time, leaving 9 tons. How many tons is there in this pile of coal?
一堆煤第一次用去了(1/3)，第二次又用去了余下的(2/3)，还剩9吨，这堆煤原来有多少吨？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(2/3) * (2/3)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 - (1/3) - (4/9)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">9 / (2/9)</gadget>
<output>81/2 = around 40.5</output>

<result>81/2 = around 40.5</result>