The four football teams A, B, C, and D scored 9, 9, x, and 7 goals in the last World Cup respectively. If the mode of this set of data is consistent with the average, the median of this set of data is How many.
甲、乙、丙、丁四支足球队在上届世界杯中进球数分别为：9、9、x、7，若这组数据的众数与平均数相符，这组数据的中位数是多少．
<gadget id="calculator">9 + 9</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<result>9</result>