SELECT avg(T2.Age) FROM gymnast AS T1 JOIN people AS T2 ON T1.Gymnast_ID  =  T2.People_ID
What is the average age of all gymnasts?
SELECT avg ( T2.Age ) FROM gymnast AS T1 JOIN people AS T2 ON T1.Gymnast_ID = T2.People_ID
select avg ( t2 . age ) from gymnast as t1 join people as t2 on t1 . gymnast_id = t2 . people_id
What is the average age of all gymnasts ?