Add 6 to the numerator of (2/3), what should be the denominator to keep the size of the fraction constant?
(2/3)的分子加上6，要使分数的大小不变，分母应多少．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<result>9</result>