There are 3 different sets of numbers involved here.
A set of six, a set of two and the set of all eight.
Each set has its own mean.
mean= Total/number of numbers
Note that if you know the mean and how many numbers there are, you can find the total.
T=M×N
You can add numbers, you can add totals, but you may not add means together.
So, for all eight numbers: The total is
8×41=328
For two of the numbers: The total is 2×29=58
Therefore the total of the other six numbers is
328−58=270
The mean of the six numbers =270/6=45