Given: The average ages of (P, Q) = 13 The average ages of (Q, R) = 14 The average ages of (R, P) = 12 Concept: We will be using the concept of average. Formula used: Average age = Total age / number of people Calculation: ⇒ P + Q = 26 ---- (1) ⇒ Q + R = 28 ----(2) ⇒ R + P = 24 ---- (3) From (1) + (2) + (3), ⇒ 2(P + Q + R) = 78 ⇒ P + Q + R = 39 ---- (4) From (4) - (3) ⇒ Q = 15 years ∴ The age of the Q is 15 years.