$\begin{align}  & (i)\text{ (}X\cap Y)=X\Leftrightarrow X\subseteq Y \\ & \text{Since }X\subseteq Y,\text{ }X=Y,\text{ }X\text{ is a proper subset of }Y \\ & \text{(}X\cap Y)=X\cap X=X \\ & (ii)X\cup Y=X\Leftrightarrow X\supseteq Y \\ & X\text{ is a proper superset of }Y\text{ meaning }Y\text{ is contained in }X \\ & X\cup X=X \\\end{align}$