To find the length of the red line segment on the number line, you need to calculate the difference between its endpoints.
The endpoints of the line segment are at \(-0.75\) and \(2.5\).
To calculate the length, use the formula:
\[ \text{Length} = \text{Endpoint at positive} - \text{Endpoint at negative} \]
Substituting in the values:
\[ \text{Length} = 2.5 - (-0.75) = 2.5 + 0.75 = 3.25 \]
So, the length of the red line segment is \(3.25\).