SAT Question 3b44439b: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice D is correct. In the figure shown, the angle marked $x^{\circ }$ and the angle marked $142^{\circ }$ form a linear pair of angles. If two angles form a linear pair of angles, the sum of the measures of the angles is $180^{\circ }$. Therefore, the value of $x+142$ is $180$.