`1,` It is extremely difficult to teach children at this age.

- V-ing + O + to be + adj : làm gì thì thế nào

- It + to be + adj + to V : thế nào để làm gì

`2,` My brother is strong enough to lift a hourse.

- S + to be + adj + enough + (for O) + to V : đủ thế nào (cho ai) để làm gì

`3,` That car is too expensive for me to afford to buy.

- S + to be + too + adj + (for O) + to V : quá thế nào (cho ai) để làm gì

`4,` My son would rather play chess than fly kites.

- prefer doing st to doing st = would rather do st than do st : thích làm gì hơn làm gì

`5,` You wasted a lot of much time in watching TV.

- waste time in doing sth : tốn thời gian làm gì

`6,` This movie is worth being seen because it is extremely interesting.

- be worth doing sth : đáng làm gì

- be worth being done sth : đáng được làm gì

`7,` I have difficulty in managing to get a visa.

- have difficulty (in) doing sth : gặp khó khăn trong việc làm gì