Answer:
y = 15 , ∠ A = 78° , ∠ B = 68°
Explanation:
the exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
∠ ACD is an exterior angle of the triangle , then
∠ A + ∠ B = ∠ ACD ( substitute values )
5y + 3 + 4y + 8 = 146 ( simplify left side )
9y + 11 = 146 ( subtract 11 from both sides )
9y = 135 ( divide both sides by 9 )
y = 15
Then
∠ A = 5y + 3 = 5(15) + 3 = 75 + 3 = 78°
∠ B = 4y + 8 = 4(15) + 8 = 60 + 8 = 68°