1. He couldn't swim until he wasn't in his twenties.

=> He wasn't  able to swim until after his twenties. 

  - Công thức gốc: S + couldn't + V + until + S + wasn't/were

  - Công thức chuyển đổi: S + wasn't able to + V + until + S + after + Noun (thời gian)

2. Even though they have a car , they seldom use it.

=> In spite of having a car, they seldom use it.

  - Công thức gốc: Even though + S + V, S + V

  - Công thức chuyển đổi: In spite of + Noun/V-ing, S + V

                                                                                      $\color{blue}{\text{#tminh}}$