Here are the rewritten sentences based on the given prompts:

1. "What do you think about teenagers who dye their hair?" (thought)
→ She thought about what teenagers do regarding dyeing their hair.

2. It was quite surprising for us that he passed the exam. (surprised)
→ We were surprised that he passed the exam.

3. "If I were you, I would tell her the truth," said Phong to Khoa. (advised)
→ Phong advised Khoa to tell her the truth.

4. We don’t know how we should approach the problems. (to)
→ We need to find out how to solve the problems.

5. "Have I ever met him before?" Uapra wondered to herself. (wondered)
→ Uapra asked herself if she had ever met him before.

6. Lan has been seriously stressed due to studying hard for the upcoming exam. (resulted)
→ Studying hard for the upcoming exam has resulted in Lan being seriously stressed.

7. Dave is feeling pressured because of his parents' high expectations for his study results. (put)
→ Dave feels put under pressure by his parents' high expectations for his study results.

8. "My close friend and I had a quarrel last week, so I felt sad," said Mary.
→ Mary said she felt sad because she and her close friend had a quarrel last week.