Let x represent the numbers
The numbers more than 3 units means their distance from zero is more than 3
[tex] |x| > 3[/tex]
This implies that either
[tex] x > 3[/tex]
or
[tex] - x > 3[/tex]
[tex] \Rightarrow x < - 3[/tex]
The solution set is the inequality
[tex]x < - 3 \: or \: x > 3[/tex]
We cannot list them