Which one would you prefer? "average age ..."
Hi, Which one would you prefer? or how would you say about it in everyday conversation?

-The average age of instructors at the gym is around 22 years old which is younger than my 24 year-old brother is.

-The instructor's average age at the gym is at 22 years old. They are younger than my 24-year-old brother.

Thanks in advance.

Question

Which one would you prefer? "average age ..."
Hi, Which one would you prefer? or how would you say about it in everyday conversation?

-The average age of instructors at the gym is around 22  years old which is younger than my 24 year-old brother is.

-The instructor's average age at the gym is at 22 years old. They are younger than my 24-year-old brother.

Thanks in advance.

Answer

"Average age .. is around" would be correct but not "average age .. is at."
Meanwhile, the "is" in "24 year-old brother is" would be unnecessary so you can drop it.

"The average age of instructors at the gym is around 22 years old, which is younger than my 24 year-old brother."

You correctly switched between "old, which" to join to sentences and "old. They are" to separate the two. Together or separate are both correct in the forms you used.