84/3= 28 This means that one brother is 28 years old. The brothers ages at this point are 28~28~28. subtract 1 from one brother and add it to another brother and you get: (28-1)~28~(28+1) or 27~28~29
27+28+29= 84 so the brothers are 27 years old, 28 years old, and 29 years old.
I hope this helps.