[SSJKarma]

i'm asking a really big question here ok !

9 year old ? that cannot be true even in the manga !
why ?
reason:
1 - in the serie, he is in "COLLEGE" at the begining of the buu saga ! COLEGE = minimum 17 years old

2 - "IF" he were in HIGH SCHOOL, that still doesn't make sense. HIGH SCHOOL = 11 years old.

do the math on your age and calculate the time it took you to be at HIGH SCHOOL and you'll know why this isn't possible for him to have 9 !

i would believe that 18 years old would be a good answer !
let me try and calculate from start...
beginning of DBZ = 4
sayien saga = 5
2 year after namek saga = 7
3 year training before androids = 10
1 year training hyper bolic time chamber = 11
7 year after CELL = 18

no, he's definitely 18 year old at the beginning of the buu saga !
well not exactly...
REAL AGE = 17
PHYSICAL AGE = 18

that's about it.
if you think my calculs are wrong you tell me it !

EDIT:
in the 9 movie, GOHAN IS 9 year old... but since this movie doesn't fit in the serie then we cannot use that to determined his real age !