Are there any mistakes?
1. This isn't MY pen, it's Susan's.
2. I think this book is YOURS.
3. This isn't your suitcase, it's OURS.
4. Where's Mary? I think these are HER gloves.
5. These keys are MINE.
6. They showed us all THEIR holiday photographs.
7. These seats are THEIR, not ours. We're over there.
8. Is this YOUR bag?
9. This isn't my jacket. It's HERS.

If you can find mistakes, please tell me why is it a mistake :)

Question

Are there any mistakes?
1. This isn't MY pen, it's Susan's.
2. I think this book is YOURS.
3. This isn't your suitcase, it's OURS.
4. Where's Mary? I think these are HER gloves.
5. These keys are MINE.
6. They showed us all THEIR holiday photographs.
7. These seats are THEIR, not ours. We're over there.
8. Is this YOUR bag?
9. This isn't my jacket. It's HERS.

If you can find mistakes, please tell me why is it a mistake :)

Answer

Also, the last sentence should say 'why it is a mistake' because it's not a question. Everything else is great!

Answer

Number 7 should be 'theirs' because you don't have a noun after.