Сделай эти предложения отрицательными. Her hair was long last year. We were in the living room. The book was very interesting.

В прошедшем времени Past Simple отрицательные предложения с глаголом to be (was, were) образуются путем добавления частицы not к глаголу - was not, were not. Сокращенная форма будет wasn`t, weren`t.

Her hair wasn`t long last year. We weren`t in the living room. The book wasn`t very interesting. She wasn`t in London last month. It wasn`t very cold. Jim and Peter weren`t lost in the forest last summer.