Найдите ошибку в предложении. 1-There is three mice on the floor. 2-Are there a mirror in your room?3-He have got a room of his own.

1). There are a three mice on the floor.

Construction "there is/are". The subject "three mice" is in the plural form.

2). Is there a mirror in your room?

Construction "there is/are". The subject "a morrow" is in the singular form.

3). He has got a room of his own.

Construction "have got". "Has" is used when the subject is "it, he, and she".