The median of a set of numbers is obtained by arranging all the numbers in ascending order then finding for the number located at the center. In a odd set of numbers, the median is easily located by finding the number at the center, however for an even set of numbers, the median is calculated by taking the average of the 2 numbers at the center.
In this case, there is an even set of numbers (6 numbers). Therefore the median can be calculated by taking the average of the 2 numbers at the center. In this case, x is one of the center numbers. The location of x can only be either at the left or right of number 12. Therefore, 12 is the other center number. Calculating for x:
Median = (x + 12) / 2
11 = (x + 12) / 2
22 = x + 12
x = 10 (ANSWER)