SAT Question 3b225698: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice C is correct. It's given that triangle $XYZ$ is similar to triangle $RST$, such that $X$, $Y$, and $Z$ correspond to $R$, $S$, and $T$, respectively. Since corresponding angles of similar triangles are congruent, it follows that the measure of $\angle Z$ is congruent to the measure of $\angle T$. It's given that the measure of $\angle Z$ is $20^{\circ }$. Therefore, the measure of $\angle T$ is $20^{\circ }$.