There are 6 observations i.e. even no. of observations
So, median will be:
\(\frac{(3rd\,observation\,+\,4^{th}\,observation)}{2}\)
Arranging in increasing order:
20, 25, 28, x, 33, 34
If we put any other number at 4th position the n, we will not get the median = 29
So, \(\frac{28+x}{2}=29\)
28 + x = 58
x = 58 – 28
= 30