Answer:
46°
Step-by-step explanation:
When secants intersect each other and a circle, the external angle (A) is half the difference of the intercepted arcs:
∠A = (arcDC -arcBC)/2
12° = (arcDC -22°)/2 . . . . . . . fill in the given numbers
24° = arcDC -22° . . . . . . . . . multiply by 2
46° = arcDC . . . . . . . . . . . . . add 22°
