Since the segment is completely horizontal we need not to use formula for computing the length of a segment in 2D euclidean space.
Instead we can simplify the problem to a single dimension, only considering the x-coordinates of the endpoints of the segment.
The x-coordinates are -5 and 3.
Subtracting and applying absolute value yields the answer,
[tex]\mathrm{abs}(-5-3)=\boxed{8}[/tex].
Hope this helps.
