"Where is your house, Sam?"
Translation:أَيْن بَيْتَك يا سام؟
It seems like: Duo uses some dialects that are familiar in some Arab countries. But, I am not sure.
In short, if we follow the standard Arabic grammar for the above statement, "where is your house, sam?" is "2aina baituka yaa sam?"
أين بَيْتُكَ يا سام؟
Update: I am sure now that Duolingo doesn't teach us 100% standard Arabic but is mixed up with some dialects, it is said in their official blog.