"C'est la cravate de mon beau-frère."
Translation:This is my brother-in-law's tie.
you will find, that some language versions are marked incorrectly although they are correct... because Duo is updating the course for our benefit the database needs to be adjusted. this is why this discussion forum is so valuable...so if things are not functioning they need to be reported. the moderators are helping too. yes it is about learning a language.... and sometimes it is annoying and frustrating... but I am thankful that this course is free and the people running it trying their best.
I'm not a native, but it sounds worse (to me) than the tie of my brother-in-law, which is not considered correct by Duo. Why? I believe huge work should be done in the domain of the possessive constructions in English. We are studying French here, and all acceptable English translations should be acceptable! (maybe some are more English than others but that's not our goal in this course)
This course is "French for English Speakers". So if you are not well acquainted with natural expressions in English, you may gravitate toward literal translations (la cravate de mon beau-frère, the tie of my brother-in-law). It is grammatically correct but awkward English. It's true that you are not here to learn English because it is expected that you already know it.
You have chosen to rewrite the sentence when no rewrite is necessary. If you know the sentences are equivalent, you don't need Duo to give you a "Good Job" for every variation, do you? When the more direct translation will serve, that's all you need. If it is not challenging enough for you, try to come up with 5 different ways to say this correctly and naturally in both languages.
No, we don’t need “good job” when we’re right, but nor do we need Duo to tell us that a perfectly good English expression is incorrect. “ This tie is my brother-in-law’s” is no less correct than “this is my brother-in-law’s tie". And if you want to get really picky it should be “this is my brother’s-in- law” tie.
I chuckled when I saw "This is the tie of my brother in law". UK comedy fans may well be transported back to the '80s wartime television series 'Allo, 'Allo starring Gordon Kaye, which makes much play on this French construction, with characters using such sentences frequently. The French had their revenge, though, mocking the British airmen's attempts at French in phrases like "Good moaning".