Ответ:

- Was Sam having supper at 7 o'clock yesterday? - Yes, he was.

- Were Ann and Betty listening to music at 5 o'clock yesterday? - No, they weren't.

- Were Ann and Betty doing their homework at 6 o'clock yesterday? - No,

they weren't.

Were Ann and Betty having supper at 7 o'clock yesterday? - Yes, they were.

Was Fred listening to music at 5 o'clock yesterday? - No, he wasn't.

Was Fred doing his homework at 6 o'clock yesterday? - Yes, he was.

Was Fred  having supper at 7 o'clock yesterday? - No, he wasn't.