Rajeev's age after 15 years will be 5 times his age 5 years back. What is the present age of rajeev?

Let Rajeev's present age be  x years.

Rajeev's age after 15 years = (x + 15) years.

Rajeev's age 5 years back = (x - 5) years

Then ATQ, 

x + 15 = 5 (x - 5)

x + 15 = 5x - 25

=> x = 10

Hence, Rajeev's present age = x = 10 years.