31. Most teenagers enjoy surfing the Internet for informatuon and entertainment.

Enjoy doing sth -> thích làm gì

surf (v) : lướt (thông tin) (mạng)

sau for + N

32. He asked me if I could help him with his work.

Câu tường thuật dạng câu hỏi yes/no : S + asked O + (that) + if/whether + V (lùi thì) + ... 

`30`. Most teenagers enjoy surfing the internet for information and entertainment.

`-` S + enjoy + V-ing: ai đó yêu thích làm gì..

`-` Surf the internet: lướt mạng

`-` For + N(danh từ/Ving)

`31`. He asked me if I could help him with his work.

`@` Câu tường thuật Yes/No questions:

`-` S + asked/wondered/wanted to know + (O) + if/whether + S + V(lùi thì)

`-` Lùi thì: can `->` could

`-` Đổi ngôi: you `->` I