Ответ:

1. There are four chairs in the living room

2. There is one mug on the table

3. There are two windows in the room

4. There is one beroom in the flat

5. There is one student in the classroom

6. There aren't three dogs in the garden

7. There isn't one pen in the pencil case

8. There aren't six apples on the table    

Объяснение:

Используем «there is» для единственного числа, а «there are» для множественного. Сокращать можно по-разному, но обрати внимание на вариант с «are»:  

there is not = there's not = there isn't / there are not = there aren't.