SAT Question 0d3f51dc: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice D is correct. It's given that line $m$ is parallel to line $n$, and line $t$ intersects both lines. It follows that line $t$ is a transversal. When two lines are parallel and intersected by a transversal, exterior angles on the same side of the transversal are supplementary. Thus, $x+33=180$. Subtracting $33$ from both sides of this equation yields $x=147$. Therefore, the value of $x$ is $147$.