Here are the rewritten sentences based on your prompts:

1. There is a TV in my room.
--> My room has a TV.

2. There are 30 students in her class.
--> Her class has 30 students.

3. The building is big.
--> It's a big building.

4. She usually walks to school.
--> She usually walks.

5. How much is this big?
--> How much does this cost?

Let me know if you need any further assistance!