Denote the average of the six numbers as n. This will be an even number and the six odd numbers are:
n−5,n−3,n−1,n+1,n+3,n+5
Then:
204=(n−5)+(n−3)+(n−1)+(n+1)+(n+3)+(n+5)=6n
Divide both ends by 6 and transpose to find:
n=2046=34
So the six odd numbers are:
29,31,33,35,37,39