Here are the conversions for each sentence:

1. Hoa started to work out in 2012. => Hoa has **been working out since 2012**.
2. They are going to pick him up at the airport tomorrow. => He **is going to be picked up at the airport tomorrow**.
3. The last time my dad went by bus was three years ago. => My dad **has not gone by bus for three years**.
4. This house isn’t as dusty as that one. => That house **is dustier than this one**.
5. I don’t know what I should do to help him out. (To do) => **To help him out, I don’t know what to do**.
6. The boys asked me: "Do you feel stressed sometimes?" => The boys **asked me if I felt stressed sometimes**.
7. Nobody in my family is as beautiful as Lan. => Lan **is more beautiful than anyone in my family**.
8. Our friends have spent their weekends in an entertainment center for 2 hours. => Our friends **began spending their weekends in an entertainment center for 2 hours**.
9. Road dust may affect our eyes very badly. => Our eyes **may be affected very badly by road dust**.
10. Don’t go out at rush hours or you will get stuck. => If **you go out at rush hours, you will get stuck**.