Answer
$(A\cup B)'=\{c, d, e, f\}$
Work Step by Step
We are given:
$U = \{a, b, c, d, e, f, g, h\}$
$A = \{a, g, h\}$
$B = \{b, g, h\}$
$C = \{b, c, d, e, f\}$
We need to determine $(A\cup B)'$
The union of sets $A$ and $B$ ($A\cup B$) is a set that has all the distinct elements of both $A$ and $B$.
$A\cup B=\{a, b, g, h\}$
The ($'$) outside of the bracket indicates that we need a complement set: the result set should contain the elements in the universal set $U$ that are not in $(A\cup B)$.
$(A\cup B)'=\{c, d, e, f\}$
