What is the value of x? º A triangle with base on an extended line. Two angle measures are given. Top interior angle is twenty-eight degrees. Lower left exterior angle is seventy-one degrees. Lower right interior angle is labeled x degrees.

All interior angles of a triangle must have a sum of 180°.

Interior angle of a triangle and its corresponding exterior angle must have a sum of 180° when its line is extended.

Top interior angle is 28°

Lower left exterior angle is 71°

Lower right interior angle is x°

Get the left interior angle.

Exterior angle + Interior angle = 180°

71° + Interior angle = 180°

Interior Angle = 180° - 71°

Interior Angle = 109°

Top Interior angle + Left Interior Angle + Right Interior angle = 180°

28° + 109° + x° = 180°

x = 180° - 28° - 109°

x = 180° - 137°

x = 43°

The lower right interior angle is 43°