1 Olga's brother is ten.
2 Nikita has got a guitar.
3 Oleg's pet is in the box.
4 Inga has got a black jacket.
6 Is Misha's kitten happy?- No, it isn't.
7 Is Misha happy?
8 Misha's pet can pay. (проверьте глагол pay. Может, play? Он по смыслу больше подходит)
9 Misha's pet is funny.
10 Who is he?- He's my brother.