"Де вагон номер дев'ять?"
Translation:Where is carriage number nine?
The English is wrong here. Not only is an article not required, it's actually wrong. Just as you wouldn't say "I live in THE flat 36", you wouldn't say "where is THE carriage number 9" (and, incidentally, "carriage" is a more natural translation of "вагон" - but I've reported that so many times I've given up on it being allowed
"Carriage" is probably correct in Britain but in Canada and the US, the term is "car," without reference to rail unless it is a discussion of different kinds of cars or a situation where people aren't aware that it's about a train.
"Where is train car number nine?" Is the correct way to say this in English. Yet, I am told it is incorrect.
No, in English no one would say "train car." They would say car, because they are clearly walking in a railway station near a train.
Справа як раз в тим, що тут дуолінго не приймає правильної відповіді, але приймає синонім, і маркерує як єдину павильну.