Solution: Assume Raghava's age be x years, his age 15 years back = x - 15, and age after 15 years = x + 15.
Then according to the problem age after 15 years = a(age 15 years back) i.e.,(x + 15) = 4(x - 15) or x + 15 = 4x -60 or 3x = 75.
.'. x = 25 years.