Add 9 to the numerator of (3/4), how much should be added to the denominator, so that the size of the fraction remains unchanged.
把(3/4)的分子加上9，分母要加上多少，分数的大小才不变．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

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

<result>12</result>