3 meters long wooden strips, use up (4/9), how much is left
3米长的木条，用去(4/9)，还剩多少
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 - (4/9)</gadget>
<output>5/9 = around 0.555556</output>

<result>5/9 = around 0.555556</result>