Question

1. (overline{cd}) is the perpendicular bisector of both (overline{xy}) and (overline{st}), and (cy = 20). find (xy).

Explanation:

Step1: Recall property of perpendicular bisector

Since $CD$ is the perpendicular bisector of $XY$, we know that $XD = DY$. Given $XD=9$, then $DY = 9$.

Step2: Calculate length of $XY$

By the segment - addition postulate, $XY=XD + DY$. Substituting the values of $XD$ and $DY$, we get $XY=9 + 9$.

Answer:

18