Answer:
72°
Explanation:
You want the measure of an angle that is 2/3 the measure of its supplement.
Setup
Let x represent the angle measure. The problem statement tells us its value is ...
x = 2/3(180 -x)
Solution
5/3x = 120 . . . . . . . . . . . . . add 2/3x, simplify
x = (3/5)(120) = 72 . . . . . . multiply by 3/5
The measure of the angle is 72°.
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Additional comment
The supplement is 180° -72° = 108°. The ratio of the angles is ...
72°/108° = 2/3