Question

If A = {…−6, −4, −2} and B = {1, 2, 3, …}, what is A ∩ B?

Answer 1

\[ \cap \]
Just means take every element in both sets.
In this case it seems there are no common elements.
so the answer is the empty set written as:
\[ \{\} \ or \ \emptyset\]

Though the pattern here isn't completely conclusive...

Answer 2

Think of the intersection as the overlap of the ven diagrams of each set.