Question

An angle is thrice its supplement. The measure of the angle is
(a) 120°
(b) 105°
(c) 135°
(d) 150°

Answer 1

Let the required angle be x.
Then,
$$\begin{gathered} x=3\left(180°-x\right) \\ \Rightarrow x=540°-3x \\ \Rightarrow 4x=540° \\ \Rightarrow x=135° \end{gathered}$$
Hence, the correct answer is option (c).