Final answer:
In set theory, the expression (X ∪ Y) ∩ X simplifies to X, as any set intersected with itself is the set itself.
Step-by-step explanation:
The question involves set theory and algebra and asks to express (X ∪ Y) ∩ X in its simplest form. Using the properties of set operations, specifically the intersection and union, we can simplify this expression. The expression (X ∪ Y) ∩ X can be simplified to just X because the intersection of a set with itself always equals the set itself, and the union of set X with any set will include all elements of X.