A8. Alex chooses three from the six primes 2003, 2011, 2017, 2027, 2029 and 2039 . The mean of his three primes is 2023 .
What is the mean of the other three primes?
Solution
2019

The sum of the six primes is $2003+2011+2017+2027+2029+2039=12126$.
The sum of the three primes which Alex chooses is $3 \times 2023=6069$.
Therefore the mean of the other three primes is $\frac{12126-6069}{3}=\frac{6057}{3}=2019$.