tenses - direct speech vs. reported speech

I'm an English teacher. I have a question about REPORTED SPEECH - PAST SIMPLE

In the book that we use there are two similar direct questions but the answers are different. I am confused, can you help me?

DIRECT SPEECH

Ned: How old were you when you decided to become an astronaut?

Mr. Nash: I was 12 years old and I was in a physics class.

REPORTED SPEECH

Ned asked Mr.Nash how old he was when he decided ...

Mr. Nash said he had been 12 and he had been in a physics class.

Why did we use past simple in the first one then past perfect in the second?

Answer

The first example was quoting Mr. Nash. Those were his words. Per Wikipedia:

Direct or quoted speech is spoken or written text that reports speech

or thought in its original form phrased by the original speaker

The second example features, as it says, reported speech -- that is, the writer is telling what Mr. Nash said, not repeating his exact words. This is also called indirect speech. Per Wikipedia:

[indirect speech] is a means of expressing the content of statements,
questions or other utterances, without quoting them explicitly as is
done in direct speech.

Hope this helps.