Part 1
[tex]D \cup E[/tex] denotes the union of the two sets (in other words, all the elements in both sets).
This means it is [tex](-\infty, 4) \cup [7, \infty)[/tex]
Part 2
[tex]D \cap E[/tex] denotes the elements shared between both sets.
This means the answer is [tex](4, 7][/tex]
