Brother is $4$ years older than sister. Sum of ages $= 30$. Sister's age is

Brother is $4$ years older than sister. Sum of ages $= 30$. Sister's age is
  1. $13$
  2. $17$
  3. $15$
  4. $11$

Solution

$2x + 4 = 30 \Rightarrow x = 13$.

Asked in: IMO

Practice more LINEAR EQUATIONS IN ONE VARIABLE questions on Aicharya