Ответ:

2) I'm not old enough to drive a car

3) These jeans are too wet to wear

4) His car is too slow

5) He is not generous enough to pay for my coffee

6) (correct)

7) He isn't popular enough to win the award

8) She is too impatient to wait

9) You are not optimistic enough about your future.

Объяснение:

(not) too smth and (not) smth enough can be used interchangeably.

слишком что-то и не достаточно что-то можно использовать попеременно.

6 предложение у вас правильно.