When I was 7, I ___ skate.

1. The Russian sentence "Когда мне было 7 лет, я не умел кататься на коньках" translates to "When I was 7, I could not skate.".
2. The word "не умел" signifies a lack of ability in the past.
3. The modal verb "could not" expresses past inability.
Answer: could not