We have that the intersection means the set of elements that are in X and Y in this case, so we have that
[tex]\begin{gathered} X\cap Y\text{ = }\lbrace15,\text{ 9, 11}\rbrace\cap\lbrace11,\text{ 9},\text{ 2}\rbrace \\ =\text{ }\lbrace9,\text{ 11}\} \end{gathered}[/tex]The answers is: A
