Given :
Positive integers 3, 4, 5, 6, 6, 7, and x are all equal.
To Find :
The mean, median, and unique mode are all equal , find x.
Solution :

Median is the middle number in sorted list.
So, median = 6
Also, mode is the number with highest frequency.
mode = 6
So,
mean = mode = median

Hence, this is the required solution.