2 Samuel 2:10-11 CSB

10 Saul's son Ish-bosheth was 40 years old when he began his reign over Israel; he ruled for two years. The house of Judah, however, followed David.
11 The length of time that David was king in Hebron over the house of Judah was seven years and six months.a

References for 2 Samuel 2:11