She was working on the problem this time yesterday.
她昨天这时候正在解那道题。
What were you doing at this time yesterday?
昨天此时你们在干什么？
Can you tell me what they were doing this time yesterday?
你能告诉我他们昨天这时候在干什么吗？
This time yesterday, we were having an English lesson.
昨地这个时候，人们正正鄙人英语课。
He can't have been in his office this time yesterday.
昨天这个时间他不可能在他的办公室里。