Думаю, что так:
1. There are many interesting articles in this magazine.
2. There are a lot of museums and theatres in our city.
3. Is there a telephone in this room?
4. There are two windows in this room.
5. There was no tea in the cup.
6. How many articles were there in this magazine? - There were several articles there.
7. How many students are there in the classroom? - There are twenty.
8. There will be a park close to our house.
9. Was there a school on this street?
10. There are several books on the table.
11. There is a school near our house. The school is located near our house.
12. There are a couple of theatres in the city. Theatres are situated in the city centre.
13. There were flowers in the vase. The flowers were in the vase.
14. There are a lot of children in the theatre. The children are in the theatre now.
15. There are a several ways to solve this problem. The ways of this problem solving are on page 5.