Answer:
∠ 4 = 130°
Step-by-step explanation:
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
∠ 4 is an exterior angle of the triangle , so
∠ 4 = ∠ 1 + ∠ 2 ( substitute values )
11x + 9 = 6x + 6 + 4x + 14 , that is
11x + 9 = 10x + 20 ( subtract 10x from both sides )
x + 9 = 20 ( subtract 9 from both sides )
x = 11
Then
∠ 4 = 11x + 9 = 11(11) + 9 = 121 + 9 = 130°
your friend may have only calculated ∠ 1
∠ 1 = 6x + 6 = 6(11) + 6 = 66 + 6 = 72°
