A pile of 12 tons of coal is used ((())/(())), and there are 4 tons left; how many tons are used, and (1/3) is left.
一堆煤12吨，用去((())/(()))，还剩4吨；用去多少吨，还剩(1/3)．
<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">12 * (2/3)</gadget>
<output>8</output>

<result>8</result>