Question: A man is 36 years old, and his sister is 29 years old. How many years ago was it when the man was twice as old as his sister?

Answer: The man is 36 and his sister is 29; the difference in their ages is 7.

So when the man was twice as old as his sister, she was 7 and he was 14.

Since the man is now 36, that was 22 years ago.