Presumably you want to find [tex]B^C\cup A[/tex], where [tex]B^C[/tex] presumably denotes the complement of [tex]B[/tex]. We have
[tex]S=A\cup B\cup D=\{2,9,13,28,40\}[/tex]
and since [tex]B=\{9,13,28\}[/tex], we have [tex]B^C[/tex] the set of all values in [tex]S[/tex] *not* in [tex]B[/tex]; that is, [tex]B^C=\{2,40\}[/tex].
Now
[tex]B^C\cup A=\{2,40\}\cup\{2,9\}=\{2,9,40\}[/tex]
