The subject of a verb is often omitted since it is already implicit in the verb. cf. BBG 16.15.
Hence, this sentence;
και ηρωτησαν αυτον και ειπαν αυτω
Is translated this way;
and they asked him and said to him…
It is translated this way because ηρωτησαν is third person, plural. The word “they” is not in the Greek; it is, however, implied in the verb ηρωτησαν. If the verb were third person, singular, then it would be translated like this:
και ηρωτησεν αυτον και ειπεν αυτω
and he asked him and said to him…
