Exegesis:

kai epērōtēsen tis auton archōn ‘a certain man of the ruling class asked him.’ For eperōtaō cf. on 2.46. archōn is used here in a general sense and denotes a person who belongs to the important and influential groups that have the ruling functions in society.

didaskale agathe ‘good teacher.’

ti poiēsas zōēn aiōnion klēronomēsō lit. ‘(by) doing what shall I inherit eternal life?,’ cf. on 10.25.

Translation:

Ruler, preferably, “a man of high standing” (The Four Gospels – a New Translation), ‘a prominent man’ (Leyden, Nieuwe Vertaling), un notable (Bible de Jérusalem).

Good Teacher, or shifting to an attributive clause, ‘teacher, you who are good.’ In this verse good is used in the sense of ‘kind,’ ‘generous,’ but in v. 19 it refers to moral perfection. Where one term covering both meanings is not available considerable difficulty may arise, since Jesus’ reply in v. 19 takes up the same term but gives it a slightly different meaning. It may then be possible, however, to qualify the term in v. 18, e.g. ‘good of heart,’ i.e. kind (Batak Toba), but to use it without qualification and in a more absolute sense in v. 19. If this also proves impossible, the term for moral goodness, or perfection, is best used in both verses.

Inherit eternal life, see on 10.25 and references.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.