The mean of a set of data 1, 2, 3, x, 5, 9 is 4, what is the median of this set of data.
一组数据1，2，3，x，5，9的平均数是4，这组数据的中位数是多少．
<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">1 + 2 + 3 + 5 + 9</gadget>
<output>20</output>

<gadget id="calculator">24 - 20</gadget>
<output>4</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<result>7/2 = around 3.5</result>