Answer:
[tex]x=45°[/tex]Step-by-step explanation:
Given that supplementary of an angle is 3 times its complementary angle. Let x be the angle measured.
Therefore, the supplementary angle of x will be 180-x and the complementary angle of x will be (90-x). If the supplementary angle is 3 times the complementary angle:
[tex]\begin{gathered} 180-x=3(90-x) \\ 180-x=270-3x \\ 3x-x=270-180 \\ 2x=90 \\ x=45° \end{gathered}[/tex]