Xiaoqiang's birthday cake was eaten (4/5), how much is left to eat.
小强的生日蛋糕被吃掉了(4/5)，还剩下多少没有吃．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>