As Sum of the Three Angles in a Triangle = 180°
We can write as :
Angle (1) + 40° + 90° = 180°
Angle (1) + 130° = 180°
Angle (1) = 180° - 130°
Angle (1) = 50°
As Angle (2) and 90° are Vertically opposite Angles :
Angle (2) should be Equal to 90°
Angle (2) = 90°
Angle (2) + Angle (3) + 30° = 180°
90° + Angle (3) = 30° = 180°
Angle(3) + 120° = 180°
Angle(3) = 180° - 120°
Angle(3) = 60°
As Angle (3) and Angle(4) are Vertically opposite Angles :
Angle (4) should be Equal to Angle(3)
Angle (4) = 60°
Angle(4) + Angle(5) + 60° = 180°
60° + Angle(5) + 60° = 180°
Angle(5) + 120° = 180°
Angle(5) = 180° - 120°
Angle(5) = 60°
As Angle (5) and Angle(6) are Vertically opposite Angles :
Angle (6) should be Equal to Angle(5)
Angle (6) = 60°
Angle(6) + Angle(7) + 20° = 180°
60° + Angle(7) + 20° = 180°
Angle(7) + 80° = 180°
Angle(7) = 180° - 80°
Angle(7) = 100°