Was/were Tom at school yesterday? No .. / He ....
Was Tom at school yesterday? No, he wasn't. He was in bed
Was/were you at home yesterday? No... I ......
Were you at home yesterday? No I wasn't. I was on the beach
Was/were Mum working on Sunday?
Was Mum working on Sunday? No, she wasn't. She was (relaxing/sitting) in the garden