R-Squared Symmetry: Regressing Y on X vs X on Y

Medium statistics interview practice: R-Squared Symmetry: Regressing Y on X vs X on Y.

Consider two variables $X$ and $Y$. You perform two simple linear regressions: first regressing $Y$ on $X$, then regressing $X$ on $Y$. What is the relationship between the $R^2$ values from these two regressions?

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