Answer:
y = 10 , ∠ C = 40° , ∠ D = 76°
Explanation:
the exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
∠ DEF is an exterior angle of the triangle , then
∠ C + ∠ D = ∠ DEF , that is
4y + 7y + 6 = 116
11y + 6 = 116 ( subtract 6 from both sides )
11y = 110 ( divide both sides by 11 )
y = 10
Then
∠ C = 4y = 4(10) = 40°
∠ D = 7y + 6 = 7(10) + 6 = 70 + 6 = 76°