First name
Edgar and Alex
School
St.Barnabas
Country
Age
10
Each number is one greater than a multiple of 3, so if they were 1 fewer, it would obviously be a multiple of 3. Because they're all 1 greater than a multiple of 3 and you pick three of them, it would be 3 greater than the multiples of three that they're 1 greater than, so it would end up being a multiple of 3 anyway.