Add 3 to the numerator of (6/18), if the size of the fraction remains the same, how much should be added to the denominator
(6/18)的分子加上3，要是分数的大小不变，分母应加上多少
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

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

<result>9</result>