How old was Rebekah when she married Isaac?

[tonychanyt]

The Bible does not answer this with a certain number. However, we have some clues.

Abraham said to his servant (S1) who was to find a wife for Isaac in Genesis 24:

8 "If the woman is not willing to follow you, you will be free from this my oath."

The woman had to agree to the marriage.

Later S1 found Rebekah:

57 Then they [Rebekah's family] said, “Let’s call the young woman and ask her about it.” 58 So they called Rebekah and asked her, “Will you go with this man?”
“I will go,” she said.

Rebekah acted rather independently. She was a young woman old enough to decide. She could be a mature teenager. Her husband was 40 years old (Genesis 25:20).