Given the current year of 2010, if you have already celebrated your birthday, you would have been born in 2010 - 60 = 1950. If you have not celebrated your birthday yet, you would be born in 1949.
if the 17 year old has not had a birthday the current year it would be the current year - 17. (this year 2009 that would be 1992)
else, if the 17 year old allready has had a birthday the current...