Here are the answers to the questions in the exercise:

1. Mr. Hoang spent **half an hour** walking to school.
2. How much is the price of this cap? **I don't know.**
3. There are **eight hundred** stamps in Hoa's collection.
4. How heavy is the chicken? What is **its weight?**
5. How much is this book? What is **the price?**
6. Listening to music is more interesting than watching TV. I prefer **listening to music.**
7. It takes me about **two hours** each day to do my homework. I spend **two hours** doing my homework.
8. How old is your daughter? What is **her age?**
9. Listening to music is more interesting than watching TV. I prefer **listening to music.**
10. Hoa spends **thirty minutes a day** practicing the piano.
11. How much is your new bike? How much **does it cost?**
12. My family has four people. There are **four members.**
13. How much is this dictionary? How much **does it cost?**
14. What is your father's age? How old **is he?**
15. It took me **two hours** to get to Vinh city by car. I spent **two hours** traveling.

Feel free to ask if you need further assistance!