Образуйте притяжательный падеж с -`s там где это возможно 1)the rules of his room 2)the dog of den 3)the flat of his brother 4)the best room of my flat 5)the friend of her sister 6) the day of masha

1) The rules of his room. 
2) Den's dog. 
3) His  brother's flat . 
4) The best room of  my flat. 
5)  Her sister's  friend.
6)  Masha's day.