Let the ages of Ani, Biju, Dharam and Cathy be a, b, c and d respectively.
Given, ages of two friends Ani and Biju differ by 3 years.
Ani’s father Dharam is twice as old as Ani and Biju as twice as old as his sister Cathy.
The ages of Cathy and Dharam differ by 30 years.
a – b = 3
c = 2a and b = 2d
c – d = 30
Solving the above four equations
⇒ 2a – b/2 = 30
⇒ 2a – a/2 + 3/2 = 30
⇒ a = 19
Thus, b = 16 years
