University of South Carolina High School Math Contest/1993 Exam/Problem 23
Problem
The relation between the sets

and

is

Solution
Every element of is a multiple of 4, and any multiple of 4 is an element of
(set
and choose
as needed). Every element of
is also a multiple of 4. If
is an integer,
so that every multiple of 4 is an element of
. Since
and
have the same elements, they are the same set:
.