"Your boys read a newspaper."
Translation:Tes garçons lisent un journal.
Because "boys/garçons" is a plural, so it needs that the possessive adjective is also plural: VOS. Remember that in French, the possessive adjective does not agree with the owner but with the object.
"Vous" is the formal version of "you", like "tu" is the informal version. "Vos" is the plural possessive, meaning "your", when talking about multiple things.
Because "votre" is used in front of singular nouns:
what about using "les nouvelles" instead of "journal"? It wouldn't be as specific as "newspaper" but would I still be able to say that in french?
Nowadays, you can read "les nouvelles" on your laptop or on your smartphone, so "les nouvelles" cannot be synonymous with "newspaper".
Duo does not expect learners to adapt the sentences proposed, but to translate them as close as possible to the original version, whenever it is possible.
Why isn't "Vos gars" acceptable? I thought it more nicely captured the informal tone of the sentence. Boy in English is relatively informal.
Why isnt "ses garçons..." accepted? What is the difference between ses and tes?
"ses" is the plural possessive for 3rd person singular = "his" or "her" in front of a plural noun.
"tes" = your
aren't they a bit young? or is it a kind of familiar "boys" said by an older person?!