Answer:
∠ ABC = 55°
Step-by-step explanation:
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
∠ ABD is an exterior angle of the triangle , then
6x + 5 = x + 45 + 3x
6x + 5 = 4x + 45 ( subtract 4x from both sides )
2x + 5 = 45 ( subtract 5 from both sides )
2x = 40 ( divide both sides by 2 )
x = 20
Then
∠ ABD = 6x + 5 = 6(20) + 5 = 120 + 5 = 125°
∠ ABD and ∠ ABC are adjacent angles and are supplementary, thus
∠ ABC = 180° - ∠ ABD = 180° - 125° = 55°
