Ответ:

They will already be leaving for Chicago by then next week, the time is now 12 o'clock.

Mary has been working since 9 o'clock. Time to take a break.

By 7 o'clock John will be writing his article for 3 hours without interruption.

The boys had been fighting for 10 minutes when the teacher entered the classroom.

Yesterday the Petrovs were packing all day.

Tom is happy because he won the prize.

When Mom returned yesterday, he hadn't done his homework yet.

While mom was preparing dinner, the children were doing their homework.