If the degree measure of an angle is 40° less than 3 times the degree measure of its supplementary angle, what is the degree measure of the angle?

Let the angle be x°, so its supplementary angle is (180 − x)°. The angle is 40° less than 3 times its supplement, so x = 3(180 − x) − 40. Solving gives x = 500 − 3x, so 4x = 500 and x = 125°. The angle measures 125° (choice C).

AI-written and checked against the verified answer.