What are the dictinct ages of the department heads?
select distinct t1.age from management as t2 join head as t1 on t1.head_id = t2.head_id
List the ages of the heads who are acting.
select distinct t1.age from management as t2 join head as t1 on t1.head_id = t2.head_id where t2.temporary_acting = 'Yes'