If the average age of Dinesh and Mahesh is 16 yr, the average age of Mahesh and Rahul is 13 yr and the average age of Dinesh and Rahul is 14 yr, then what is the age of Mahesh?

Let ages of Dinesh, Mahesh and Rahul be D, M and R, respectively.
Then,
D + M = 2 x 16 = 32 ...(i)
M + R = 2 x 13 = 26 ....(ii)
D + R = 2 x14 = 28 ....(iii)
On adding Eqs. (i), (ii) and (iii), we get
2(D + M + R) =86
⇒ D + M + R = 43 ....(iv)
On subtracting Eqs. (iii) from Eq. (iv), we get
M = 43 - 28
∴ M = 15 Yr