Answer:
Step-by-step explanation:
The rule is that the exterior angle (ACD) is equal to the sum of the remote interior angles (the two marked angles on the right).
You are expected to use this relation to write and solve an equation.
exterior angle = angle D + angle B
(2x +16) = 58 + (x+12)
2x +16 = x +70
x + 16 = 70
x = 54
Then angle ACD is ...
angle ACD = (2x +16)° = (2·54 +16)°
angle ACD = 124°
