Exegesis:

en tō nomō ‘in the law,’ cf. on 2.22.

pōs anaginōskeis lit. ‘how do you read,’ or, ‘how do you recite,’ i.e. in the worship service in the synagogue, a rabbinical formula used when a scripture quotation is called for. The latter rendering appears to be slightly preferable. pōs refers to the content of what is read, cf. Translator’s New Testament.

Translation:

He said, i.e. Jesus said/asked.

What is written in the law, see on 2.22f.

How do you read, or, “what do you read there” (Translator’s New Testament), ‘how/what do you (usually) read aloud, or, recite.’ For to read cf. on 4.16.

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.