Sure! Here are the rewritten sentences with unchanged meanings:

1. Nam stated that his uncle often plants the vegetables in the afternoon.
2. She mentioned that her uncle would not plant the vegetables tomorrow afternoon.
3. Nga reported that Mr. and Mrs. Pike had just read those newspapers.
4. She mentioned that she often listens to music at night.
5. Lan's mother stated that her daughter usually brushes her teeth before meals.
6. They mentioned that they had to do the assignments now.
7. Lan says that her sister seldom rides a bike to school.
8. She said that students at secondary school and high school rarely sing English songs.
9. They stated that their teacher sometimes explains the difficult lessons.
10. My Geography teacher says that the Earth moves around the sun.
11. Nam stated that he was doing his homework at that moment.
12. My father told me that I should stop smoking.
13. Na asked if Tom would be here tomorrow.
14. Ngoc told me that she was having dinner when she came.
15. He told her that he would take her home.
16. The little girl said that she hadn't done her homework.