"The seventh car is not in front of the garage, but in the garage."

Translation: A hetedik autó nem a garázs előtt áll, hanem a garázsban.

[Evolita]

"a hetedik auto nem a garazs elott, hanem a garazsban van." should be accepted. "Is" can be translated to "van" so this translation is just as correct. Reported, btw.

[ElisabethS832761]

I'm guessing the word "all" means that the car is "parked" in the garage but can it not be left out. I left out the word "áll" and Duo did not accept it.

[SusanRankin1]

Oh dear... why dont I need a second elott one before and one after a garazs ?

[mizinamo]

why dont I need a second elott one before and one after a garazs ?

előtt doesn't come before anything; it comes after things. It's a postposition.

So you can have two if there are two things for it to come after, e.g. az előtt a garázs előtt "in front of that garage".

But there is no az "that" in Duo's sentence, so there's no additional thing for an előtt to come after.