Here are the rewritten sentences based on your request:

1. **Mr. Nghia** has a new blue car.
2. **It took** her an hour to get to school due to the traffic jam.
3. The train is more expensive than the subway.
**The subway isn’t as expensive as the train.**
4. He didn’t study; therefore, he failed his math test.
**He failed** his math test due to a lack of study.
5. Even though he was old, he worked very hard.
**In spite of** his age, he worked very hard.
6. Jack demonstrates more creativity than other students in his class.
**Jack is the** most creative in his class.
7. “How did you arrive at your friend’s house yesterday, Nam?” she inquired.
**She asked** Nam how he got to his friend's house.
8. She doesn’t have any sugar, so she can’t bake a cake.
**If** she had sugar, she would be able to make a cake.
9. Other oceans in the world aren’t as large as the Pacific Ocean.
**The Pacific Ocean is** the largest ocean in the world.
10. Due to his friend’s absence, he has to copy the lesson for her.
**Because** his friend is absent, he must take notes for her.