Answer: 140°
Step-by-step explanation:
∠C = 40°
BC = unknown ⇒ ∠D = x
CD = BC ⇒ ∠B = ∠D = x
Triangle Sum Theorem states: ΔBCD = ∠B + ∠C + ∠D = 180°
x + 40° + x = 180°
2x = 140°
x = 70°
Given: ∠EBD ≡ ∠CBD
∠EBD = 70°
Angle Sum Theorem: ∠EBC = ∠EBD + ∠CBD
= 70° + 70°
= 140°
