angles x and y are supplementary. angle x is 3 times the measure of angle y. what is the measure of angle…

Explanation:

Step1: Set up equations

Let the measure of angle $Y$ be $y$. Then the measure of angle $X = 3y$. Since $X$ and $Y$ are supplementary, $X + Y=180^{\circ}$, so $3y + y=180^{\circ}$.

Step2: Solve for $y$

Combine like - terms: $4y = 180^{\circ}$. Then $y=\frac{180^{\circ}}{4}=45^{\circ}$.

Step3: Find the measure of angle $X$

Since $X = 3y$, substitute $y = 45^{\circ}$ into the equation. So $X=3\times45^{\circ}=135^{\circ}$.

Answer:

D. $135^{\circ}$