Question 114792
Let x be the age when the man died.

Then (1/4)x + (1/5)x + (1/3)x + 13 = x  ( Since, a fourth of his life was lived as a boy can be written as (1/4)x.

Solve the above equation. 

(1/4)x + (1/5)x + (1/3)x - x = -13

(1/60){15x +12x + 20x - 60x}= -13   ( Take LCM)
-13x = -780
x = 60.

The age of death is 60