Let the age of the girl = 'x' years.
So, the age of her younger sister = (x 4) years.
Thus, the age of the brother = (x 4 4) years = (x 8) years.
ATQ:
⇒ (x 4) + (x 8) = 16
⇒ x + x 4 8 = 16
⇒ 2x 12 = 16
Adding 12 to both sides, we get
⇒ 2x 12 + 12 = 16 + 12
⇒ 2x = 28
Dividing both sides by 2, we get
⇒
⇒ x = 14
Thus, the age of the girl = x = 14 years, the age of the younger sister = x 4 = 14 4 = 10 years,
and the age of the younger brother = x 8 = 14 8 = 6 years.