1 Their house is very modern.
2 Is Ben your brother?
3 Are these books hers?
4 This camera isn't mine.
5 This little puppy isn't ours.
6 Tom and Sarah are my friends.
7 What is his address?
8 What's her phone number?
9 Is this football his/her?
В 9 подходят оба,видимо ты неправильно написал.