Here's how you would figure it out: Take the current year (2009) and subtract the year of birth (1975). You would be 34 years old.
How Old Would You Be If You Were Born In 1975?
If you are born in 1975 then in this year of 2018 you'll be 43 years old.
I always calculate my age through this tremendous age calculator , here you can easily gets all the ultimate results of age.
Hope that helped!