=>
I/
1. The white dress is not as expensive as the black dress./ The white dress is cheaper than the black dress.
-> so sánh hơn tính từ ngắn : adj-er than
-> so sánh bằng : as adj as
2. You don't have to bring an umbrella./You don't need to bring an umbrella.
-> don't have to V : không phải làm gì
-> don't need to V : không cần làm gì
II/
1. A tourist travels more cheaply than a businessman.
-> travel là động từ -> so sánh hơn của trạng từ more adv than
2. We hold the traditional festivals every year although they are costly.
-> although : mặc dù
3. While I was in England, I was lucky to join the Glastonbury Festival.
-> while : trong khi