This is what was going on this time yesterday.
What were the two smileys doing this time yesterday?
The first smiley was playing the guitar while the second smiley was reading the news.
* The two smileys were doing different things at the same time in the past.
1. to talk about two actions that were in progress at the same time in the past
I was eating dinner while they were playing.
2. to talk about an action that was in progress when another action interrupted it
I was eating dinner when the telephone rang.
3. to talk about an action that was in progress at a specific time in the past
I was eating dinner at 7 o'clock yesterday.
Practice with Past Simple and Past Progressive on Wordwall:
Exercises on Past Progressive (ego4u.com)
Tests (ego4u.com)
Exercises on Simple Past and Past Progressive (ego4u.com)
one after another or at the same time: Exercise 1, Exercise 2
new or already in progress: Exercise 3, Exercise 4
just mentioning or emphasizing progress: Exercise 5, Exercise 6
mixed exercises: Exercise 7, Exercise 8
Exercises with Past Simple and Past Progressive from EnglishPage.com