Ответ:

  1. I was at the park with my family yesterday. We like going there.
  2. A: Why weren’t you at school yesterday? B: I wasn’t well.
  3. A: Were you at Sam’s party on Saturday? B: Yes, I was.
  4. He was my teacher last year but he is this year.
  5. The weather was great last week – really sunny!
  6. We weren’t at home on Monday afternoon. We always play football in the park on Mondays.

Правило: was употребляется с I, he, she, it; were — с you, we, they.