Answer:
Angle YDC = 140°
Step-by-step explanation:
15x + 5 = 80 + 6x + 6 (Exterior angle of a triangle is sum of two opposite interior angles)
15x - 6x = 86 - 5 = 81
9x = 81
Divide both sides by 9
x = 9
Angle YDC = 15x + 5 = 15(9) + 5 = 135 + 5
Angle YDC = 140°
