Were va en oraciones en plural o en singular?

Were / was son pasado del verbo ser o estar ( verb to be).

Was es usado con : i, he, she, it.

Entonces usas were con you :

1.

- You were sick last week.

Tú estuviste enferm@ la semana pasada.

(you en singular)

2.

- you were playing tennis together.

Ustedes estuvieron jugando tenis junt@s.

(you en plural).