SAT Question 055aafe7: Lines, Angles, and Triangles answer and explanation with Desmos solution

Choice D is correct. It's given that triangle $ABC$ is similar to triangle $XYZ$, where $A$, $B$, and $C$ correspond to $X$, $Y$, and $Z$, respectively. It follows that side $AB$ corresponds to side $XY$ and side $BC$ corresponds to side $YZ$. Since the lengths of corresponding sides in similar triangles are proportional, it follows that $\frac{XY}{AB}=\frac{YZ}{BC}$. Substituting $170$ for $AB$, $60$ for $YZ$, and $850$ for $BC$ in this equation yields $\frac{XY}{170}=\frac{60}{850}$. Multiplying each side of this equation by $170$ yields $XY=12$. Therefore, the length of $PARS{E}_{E}RROR:Entit{y}^{\prime }mac{r}^{\prime }notdefined,line1,column139(<string>,line1)$ is $12$.