Sure, here are the rewritten sentences:

1. There are twenty students in my class.
My class has twenty students.

2. There are twenty boys in my class.
My class has twenty boys.

3. There are two students in my class.
My class has two students.

4. There are forty girls in my class.
My class has forty girls.

5. There are two tables in my class.
My class has two tables.

6. There are sons in Land's family.
Land's family has sons.

7. There are daughters in Land's family.
Land's family has daughters.

8. There are 2 women in Lan's family.
Lan's family has 2 women.

9. There are 2 people in Binh's family.
Binh's family has 2 people.

10. There are two pens in Lan's bag.
Lan's bag has two pens.