"There is a cat at our house."
Translation:Det er en katt hos oss.
I looked this up a long time ago and what I ended up with was that the etymology of hos was hus, but hos is a preposition. So I figured it was one of those times where hos had more meaning than just "with" or "at" and in typical norwegian fashion, it was wrapped up in one word. I accepted that when I saw hos oss that it meant "with us " but in particular, "with us (at our house)"
I feel like the English sentence should be "There is a cat at our place" to differentiate between the literal, normal translation of "Det er en katt på huset vårt" and "Det er en katt hos oss" given that it's clear they want the latter answer as opposed to the former. It'd be completely acceptable and normal for Duo to ask you to translate "There is a cat at our house" as "Det er en katt på huset vårt."