Giving advice

Mark: Hey, Kelly, what's the matter? You look worried. What's the problem?
Kelly: Yes, it's my brother. I think he's stealing things. I found ten new DVDs in his room.
Mark: Wow! That's serious! What are you going to do?
Kelly: I don't know. What do you think I should do?
Mark: Well, if I were you, I'd speak to him.
Kelly: I tried that, but he didn't listen.
Mark: Then you have to try again. Come on - I'll come with you.
Kelly: OK. Thanks Mark.