Let Rakesh, Mohan and Ramesh are represented by x, y, and z respectively. Average age of x and y = 15 Average age of y and z = 12 Average age of x and z = 13 Total age of x + y = 30 ......(i) y + z = 24 ......(ii) x + z = 26 ......(iii) Subtracting (iii) from (i)y - z = 4......(iv) Adding y + z = 24 in (ii) and (iv), 2y = 28 ⇒ y = 14 Age of Mohan = y = 14 years.