Well I like math questions as they are pretty easy to figure out, though I wonder what you mean by "teenager"? The correct answer seems to be 9 and 11, as in 9 years they would be 18 and 20 (nine/tenths) and 5 years ago they were 4 and 6 (2/3rds). I'm guessing you don't consider 11 to be a "teenager" even though the number 11 is in the teens? Otherwise I'm clueless...
