Two angles whose sum is 180° are called supplementary angles. The measure of the unknown angle is 41°.
What are supplementary angles?
Two angles whose sum is 180° are called supplementary angles. If a straight line is intersected by a line, then there are two angles form on each of the sides of the considered straight line. Those two-two angles are two pairs of supplementary angles. That means, if supplementary angles are aligned adjacent to each other, their exterior sides will make a straight line.
The two of the given angles form a linear pair. Thus, the measure of the two angles together will be equal to 180°.
1.) An equation to represent the measures of the angles.
x + 139° = 180°
2.) Solving the equation to find the measures of the unknown angle,
x + 139° = 180°
x = 180° - 139°
x = 41°
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