Доброго времени суток!
1) There is a bookcase in my room (Использовал there is т.к. ед число)
2) Is there a wardrobe in your room? (Ед. число)
3) Is there a TV a video at the window? (Перечисление ед. ч)
4) Are there books on the bookshelf? (Множ. число)
5) There are three rooms in may flat (Множ. ч)
6) There are four armchairs in the living room. (Мн. ч )
Удачи