A pile of 9 tons of coal, used up (2/9), how many tons are left.
一堆煤9吨，用去(2/9)，还剩多少吨．
<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">1 - (2/9)</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">9 * (7/9)</gadget>
<output>7</output>

<result>7</result>