6. we having a fancy dress party at noon last Saturday? — Yes, we / No, we

6. we having a fancy dress party at noon last Saturday? — Yes, we / No, we

Согласно грамматике английского языка, необходимо вставить вспомогательный глагол перед подлежащим, чтобы образовать вопрос в Past Continuous (прошедшее продолженное время).

В данном случае, подлежащее - we, поэтому используем вспомогательный глагол were.

we having a fancy dress party at noon last Saturday? - Were we having a fancy dress party at noon last Saturday?

Yes, we / No, we - Yes, we were / No, we weren't.

Ответ: Were we having a fancy dress party at noon last Saturday? — Yes, we were / No, we weren't