A pencil uses up its (4/9), how much more is left than used
一支铅笔用去它的(4/9)，剩下的比用去的多多少
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 - (4/9) - (4/9)</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/9) / (4/9)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>