Let Ravi s present age be X years.
Ravi s Age after 15 Years be : (X+15) Years
Now also his age after 15 years will be four times his present age. (When Times is given means we have to product it). Therefore,
4X = (X+15)
=> 4X - X = 15
=> 3X = 15
=> X = (15/3)
=> X = 5.
Hence Ravi s Present age is 5 Years.