Answer:
96°
Step-by-step explanation:
The measure of arc EC is twice the measure of ∠DEC, so is ...
arc EC = 2×68° = 136°
The measure of arc BC is found from the sum of arcs around a circle.
BC +CE +EB = 360° = BC +136° +128°
BC = 96° . . . . . subtract 264°
