Answer
$M' \text{ or } \left\{1, 3, 5, 7, 9, 10, 11, 12, 13\right\}$
Work Step by Step
$x \in U$ and $x \not \in M$ means that the elements of the given set are in U but not in M. This is actually the definition of the complement of a set M.
Thus, the given set is equivalent to:
$M' = \left\{1, 3, 5, 7, 9, 10, 11, 12, 13\right\}$
