Here are the rewritten sentences using the words in brackets:

1. Son Tung is 1.80 m. Mr. Buong is 1.80 m, too.
→ Son Tung is **as tall as** Mr. Buong.

2. The painting is bigger than the photograph.
→ The photograph is **not as big as** the painting.

3. This painting is more expensive than my painting.
→ My painting is **not as expensive as** this painting.

4. This picture is the same as the picture in our room.
→ The picture in our room is **not different from** this picture.

5. This film is more interesting than the one we saw last week.
→ The film we saw last week is **not as interesting as** this film.

6. The journey was shorter than we thought at first.
→ The journey was **not as long as** we thought at first.