Here are the joined sentences using relative clauses:

1. The photos, which he had taken with a cheap camera, came out beautifully.
2. I’ve brought the photographs that I told you about.
3. Quang, who lives in that house, was the one you saw on the corner.
4. The birthday card, which you liked so well, has already been sold.
5. They accepted every suggestion that we made.
6. Is this the letter that you wanted me to mail?
7. I tried to read every book that the teacher recommended to me.
8. That’s the girl who Tan and Hung were talking about.
9. The flowers, which you gave to me, are in that vase.
10. Everyone congratulated me on my success at the exam, which I met them at the party.
11. She’s the woman to whom I gave the flowers.
12. He must be the boy who we saw running away.
13. The woman who won the photo contest took this picture.
14. The student who is walking with Tam is in my class.
15. Did you mail the two letters that were on my desk?