Question

the measure of an angle is 129°. what is the measure of its supplementary angle?

Explanation:

Step1: Recall supplementary - angle definition

Supplementary angles add up to 180°. Let the given angle be \(A = 129^{\circ}\) and the supplementary angle be \(x\). Then \(A + x=180^{\circ}\).

Step2: Solve for \(x\)

\(x = 180^{\circ}-A\). Substitute \(A = 129^{\circ}\) into the equation: \(x=180 - 129\).
\(x = 51^{\circ}\)

Answer:

51