This question was uploaded on 16/12/21 on social media accounts.
Solution:
By Pythagoras theorem:
\[AB = Y\frac{\sqrt5}{2}\]
By similar triangle ABC and ACD:
\[\frac{AB}{BC} = \frac{AC}{CD}\]
\[\Rightarrow \frac{Y\sqrt5/2}{Y/2} = \frac{Y}{X/2}\]
\[\Rightarrow \frac{X}{Y} = \frac{2}{\sqrt5} = \frac{2}{5}\sqrt5\]
