I do not think that " Do you see a young 1" is a correct answer.
And I think "Do you see a youth" should be correct. http://dictionary.cambridge.org/dictionary/english/youth
Based on the dictionary entry you provided, youth is only used in that sense in American English, but I'm not sure it's common enough to be considered an acceptable answer (after all, a line has to be drawn somewhere, or else we'd end up with an infinite number of accepted translations).
Anyway, please don't post comments about answers that you think should be accepted, because it's considered clutter. Report mistakes instead, so that your suggestions can reach the contributors themselves (use the "Report a Problem" button after answering a sentence). :)
Thank you! I will do so. Thank you for creating a Duolingo program for learning Hungarian!
Don't thank me, I'm not one of the creators. I'm just here to randomly help people when I can. :)
Youth (sg. n.) may be slightly more common in america, but is not in any sense a kind of regional variation, as you so bizarrely imply. It's standard english, and means the same as "young person." I reported it.
This sentence doesn't make sense. Látsz egy fiatalt? means do you see a young? this is weird
In Hungarian, an adjective like "young" can also take the place of a noun, so it means something like "young one." Piros is "red", and to translate an English sentence like, "I see a red one", you would say Látok egy pirosat. The word "one" in the English sentence doesn't have any corresponding word in the Hungarian sentence.
Fiatal can mean "young person" when used as a noun.
Itt egy netes szótár. A melléknévi jelentésekkel kezd, de most a legalsó bekezdés az érdekes. Van pár példamondat is.
To tell the truth, I've no idea what your mother tongue is, hence my switching languages. I think a native speaker not knowing that fiatal can be used as a noun is just as unikely as a non-native speaker working their way up to level 6 on the HU->EN tree before embarking on the EN->HU one. Both are definitely possible, nonetheless.
Ha magyar vagy, akkor mondjuk érdekelne, hogy honnan származol, mert az én köreimben a fiatal kifejezetten gyakori szó, mind melléknévként, mind főnévként.