select avg(N.number) as Average
--just average from task 7
from (
    select t.team_name, count(tt.team_id) as 'Number'
    from teams as t
    join (
        select t.team_id, t.team_name
        from teams as t
        join employees as e on e.team_id = t.team_id
        where e.gender = 'F'
    ) as tt on t.TEAM_ID = tt.team_id
    group by t.team_name
    UNION
    -- just solution from task 6:
    select distinct t.team_name, '0'
    from teams as t
    where t.team_name not in (
        select distinct t.team_name
        from teams as t
        join employees as e on t.team_id = e.TEAM_ID
        where e.gender = 'F'
    )
) as N