#### Answer

$A' = \left\{2, 6, 9, 10\right\}$

#### Work Step by Step

Given:
Universal set:
$U=\left\{1, 2, 3, 4, 5, 6, 7, 8, 9, 10\right\}$
$A=\left\{1, 3, 4, 5, 7, 8\right\}$
RECALL:
$A'$ is the set the contains the elements of the universal set that are not in $A$.
Thus,
$\color{blue}{A' = \left\{2, 6, 9, 10\right\}}$