Change into indirect voice – use “was” or “would be"

Question

I have this sentence:

Mother said, "Gaurav, you will be eligible for voting when you are 18."

How do I change it into indirect voice? Which of the following is better?

Mother told Gaurav he would be eligible for voting when he was 18.

Or:

Mother told Gaurav that he would be eligible for voting when he would be 18.

You see I'm mainly confused with the use of "was" in this case. Also I would be pleased if someone explains if the use of "when" can be done as a question word when the sentence is not interrogative, for deciding if "that" has to be used in it or not.

Answer 1

In English (unlike many other languages) we do not use the so-called future tense (with "will") inside "if" or "when" clauses.

So in direct speech, the form is "when you are 18", not "when you will be 18".

Consistently with that, in indirect speech the normal form is "when he was 18", not "when he would be 18".