Subset/Examples/Abstract Example 1

Example of Subset
Let $P$ denote the set:
 * $P = \set {1, 2, 3, 4}$

Let $Q$ denote the set:
 * $Q = \set {2, 4}$

Then:
 * $Q \subseteq P$

but note that:
 * $Q \notin P$