Final answer:
The measure of the supplementary angle to a 64.3° angle is 115.7°, which is calculated by subtracting the given angle from 180°.
Step-by-step explanation:
The measure of an angle plus the measure of its supplementary angle equals 180 degrees, as they are a pair of angles that add up to form a straight line.
To find the measure of the supplementary angle when given an angle of 64.3°, you subtract the given angle from 180°.
Calculation:
Supplementary Angle = 180° - Measure of Given Angle
Supplementary Angle = 180° - 64.3°
Supplementary Angle = 115.7°