snapchat instagram total
Boys 40 50
Girls 30 50
Total 100
Boys : snapchat = 50 - 40 = 10
Girls : instagram = 50 - 30 = 20
Snapchat : 10 + 30 = 40
Instagram : 40 + 20 = 60
boys: 50/100 = 50%
boys that prefer snapchat: 10/50 = 10%
girls who prefer instagram: 20/50 = 20%