2 Kings 18:1-20:21
Now it came to pass in the third year of Hoshea son of Elah king of Israel, that Hezekiah the son of Ahaz king of Judah began to reign.
Torrey's Topical Textbook—AKJV

2 Chronicles 29:1-32:33
Hezekiah began to reign when he was five and twenty years old, and he reigned nine and twenty years in Jerusalem. And his mother's name was Abijah, the daughter of Zechariah.
Torrey's Topical Textbook—AKJV