1. There is a window in the hall. There is not a window in the hall.
2. There are armchairs in the room. There are not armchairs in the room.
3. There is a living room in the house. There is not a living room in the house.
Объяснение:
Чтобы составить отрицательное предложение, нужно добавить 'not' после 'is' или 'are'. Например, 'There is a book' -> 'There is not a book' или 'There are books' -> 'There are not books'.