Swimmers: 50 children ÷ 12 = 4.2 (you can't have a decimal so you must round up)
5 adults are need.
Dancers: 32 children ÷ 15 = 2.1 (you can't have a decimal so you must round up)
3 adults are need.
Minimum number of adults needed is: 5 for swimmers + 3 for dancers = 8 adults