Add 9 to the numerator of (3/4), what should the denominator be to keep the size of the fraction constant?
(3/4)的分子加上9，要使分数的大小不变，分母应多少
<gadget id="calculator">3 + 9</gadget>
<output>12</output>

<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<result>12</result>