The original 7 red circles accounted for the whole (7/9), now add 2 red circles, then the red circles accounted for the whole ((())/(())).
原7个红圆片占整体的(7/9)，现增加2个红圆片，这时红圆片占整体的((())/(()))．
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">7 / (7/9)</gadget>
<output>9</output>

<gadget id="calculator">9 + 2</gadget>
<output>11</output>

<gadget id="calculator">9 / 11</gadget>
<output>9/11 = around 0.818182</output>

<result>9/11 = around 0.818182</result>