After the denominator of (9/16) is tripled, how much should be added to the numerator to keep the size of the fraction unchanged.
(9/16)的分母扩大了3倍后，要使分数的大小不变，分子应加上多少．
<gadget id="calculator">27 - 9</gadget>
<output>18</output>

<result>18</result>