Well for part a, just multiply the ages by their respective frequencies, and add them and divide by 11. You would get 20.90909091, so the mean age is about 20.9.
For part b, there would be 12 players with a mean age of 22. Their ages would add up to be 12 * 22 = 264.
The original 11 players' ages add up to be 230. 264 - 230 = 34. So, the new player is 34 years old.
