The numerator of (4/9) is increased by 4. If the fraction remains the same, how much should the denominator be increased?
(4/9)的分子增加4，要是分数大小不变，分母应增加多少
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 - 9</gadget>
<output>9</output>

<result>9</result>