A piece of cake, after eating (1/5), left ((())/(())).
一块蛋糕，吃了(1/5)，还剩((())/(()))．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>