pile of 18 tons of coal, (1/3) is used for the first time, and the rest (1/3) is used for the second time, how many tons are left.
一堆煤18吨，第一次用去(1/3)，第二次用去余下的(1/3)，还剩下多少吨．
<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) * (1/3)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 - (1/3) - (2/9)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">18 * (4/9)</gadget>
<output>8</output>

<result>8</result>