This Bible contradiction is from the Skeptic's Annotated Bible.
22 years old
2 Kings 8:26 View context
Two and twenty years old [was] Ahaziah when he began to reign; and he reigned one year in Jerusalem. And his mother's name [was] Athaliah, the daughter of Omri king of Israel.
42 years old
2 Chronicles 22:2 View context
Forty and two years old [was] Ahaziah when he began to reign, and he reigned one year in Jerusalem. His mother's name also [was] Athaliah the daughter of Omri.