1 He was from Italy.
2 Were Bach and Brahms composers?
Yes, they were.
3 Were they from France?
No, they weren’t. They were from Germany.
4 Was Shakespeare a painter?
No, he wasn’t. He was a writer.
5 Were Picasso and Goya painters?
Yes, they were.
Правило очень простое: если подлежащее в единственном числе, то используем форму was, а если подлежащее во множ. числе (или в предложении два подлежащих), то нужна форма were.