Ответ:

2. When Robert finished writing his essay, he went out with his friends

3. I walked into the classroom while she was talking with the teacher

4. I used to see Gill more often

5. Brenda felt sick because she had eaten three bars of chocolate

6. We were both very bse yesterday evening: I was doing my Maths homework while Joanna was ironing

7. The Perkins didn't use to be very rich