There is a mistake in the sentence. Find the mistake and correct it

b/ There is a mistake in the sentence. Find the mistake and correct it.
1. The climate in Vietnam is different than that of England .
2. The boys said they have to bring home medals.
3. He has waited here for a quarter past six.
4. Surface is many cheaper than airmail.
5. The bicycle is such old that I don’t want to use it.