Answer:
∠AEC = 139°
Step-by-step explanation:
Since EC bisects ∠BED then ∠BEC = ∠CED = 4x + 1
∠AED = ∠AEB + ∠BEC + ∠CED = 180 ← straight angle
Substitute values into the equation
11x - 12 + 4x + 1 + 4x + 1 = 180, that is
19x - 10 = 180 ( add 10 to both sides )
19x = 190 ( divide both sides by 19 )
x = 10
Hence
∠AEC = ∠AEB + ∠BEC = 11x - 12 + 4x + 1 = 15x - 11, hence
∠AEC = (15 × 10) - 11 = 150 - 11 = 139°
