How many heads are temporary acting?
select count ( * ) from management where temporary_acting = 'Yes'
What are their names?
select t1.name from management as t2 join head as t1 on t1.head_id = t2.head_id where t2.temporary_acting = 'Yes'
What are their distinct ages?
select distinct t1.age from management as t2 join head as t1 on t1.head_id = t2.head_id where t2.temporary_acting = 'Yes'