Janet is three years older than her sister julie. janet's brother is eight years younger than their sister julie. the sum of all of their ages is 55 years.

Assume Julie is x years old

(x+3)+x+(x-8)=55                   Julie is 20 years old

3x-5=55                                 Janet is 23 years old

3x=60                                     brother is 12 years old

x=20