Answer
$\{a,c,d,e,f,h\}$
Work Step by Step
Recall the following: $x\in A\cup B$ if and only if $x\in A$ or $x\in B$. Thus, to find the union of the given sets, we must find all elements that appear in either set. This gives us: $$\{a,c,d,e\}\cup\{c,d,f,h\}=\{a,c,d,e,f,h\}$$
