An airline offers the same number of tickets for morning and night flights.  When the airline analyzed ticket sales, they determined that the ratio of the number of sold tickets to the number of unsold tickets was 3
:
5
3:5
3:5
on morning flights and
7
:
1
7:1
7:1
on night flights.  If the airline sells
581
581
581
tickets on night flights, how many unsold tickets can the airline expect on morning flights?