Answers:

6. The house is too expensive for them to buy.

->The house isn’t cheap enough for them to buy.

(S+be+too+adj+(for sb)+to V -> S+be+adj+enough+(for sb)+to V)

7. He will be absent from the class discussion tomorrow.

->I wish he wouldn't be absent from the class discussion tomorrow.

(Câu "wish" cho tương lai "will" lùi thì thành "would")

8. What a pity! She can't complete her homework.

->I wish she could complete her homework.

(Câu "wish" cho hiện tại "can" lùi thì thành "could")

9. It’s a pity, my sister gets a headache. (wish)

->I wish my sister didn't get a headache.

(Câu "wish" cho hiện tại lùi thì ht thành thì qk)

10. I feel annoyed when he talks too much.

->I wish he didn't talk too much.

(Câu "wish" cho hiện tại lùi thì ht thành thì qk)

11. Lien never goes on a camping trip.

->Lien wishes she went on a camping trip.

(Câu "wish" cho hiện tại lùi thì ht thành thì qk)