Краткое пояснение:
В английском языке в прошедшем времени (Past Simple) глагол 'to be' принимает формы 'was' (для I, he, she, it) и 'were' (для you, we, they). При отрицании добавляется 'not'. Сокращенная форма образуется путем слияния глагола и 'not'.
Пошаговое решение:
1. I was not → I wasn't
2. She was not → She wasn't
3. They were not → They weren't
4. You were not → You weren't
5. We were not → We weren't