A pile of coal has been burned (3/7), and the rest is burned ((())/(())).
一堆煤已烧掉(3/7)，剩下的是已烧的((())/(()))．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(4/7) / (3/7)</gadget>
<output>4/3 = around 1.333333</output>

<result>4/3 = around 1.333333</result>