`13.` How much do these book cost ? 

`→` How much có 3 dạng viết lại :

`+` How much is/ are + S

`+` How much + do/does + S + cost ?

`+` What is the price of + S ?

`14.` We go to work by car everyday.

`→` drive = go ___ by car

`15.` I have never met her before.

`→` This is the first time + S + have/has + VPII 

= S + have/has never + VPII + before

`16.` I haven't seen him for 2 days.

`→` Phủ định của hiện tại hoàn thành :

S + have/has not + VPII + for/since thời gian

`17.` They have worked in the garden for 30 minutes.

`→`  S + have/has + VPII + for/since thời gian

`18.` I haven't phoned her since last Sunday.

`→` Phủ định của hiện tại hoàn thành :

S + have/has not + VPII + for/since thời gian

`19.` This is the fist time I have spoken to her.

`→` S + have/has never + VPII + before

= This is the first time + S + have/has + VPII  ( lần đầu tiên làm việc nào đó )

`20.` We have become friends for 20 years.

`→`  S + have/has + VPII + for/since thời gian