Add 12 to the denominator of (3/4), if the size of the fraction remains the same, how much should the denominator be multiplied.
(3/4)的分母加上12，要是分数的大小不变，分母应乘多少．
<gadget id="calculator">3 + 12</gadget>
<output>15</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>