For a line segment you should create a right triangle by making two more lines. If this line segment is on a dot grid every line between two dots is one unit. The length of this line can be found by using the distance formula.
If the line segment is on a coordinate plane then you can do the same or use the distance formula for a line.
Sqrtx_2 - x_12 y_2 - y_12. For which points in the same quadrant as 2 -10 could Tamara use a number line to find the distance. Distance between a line and a point. Finding the Distance Between Two Points with Positive Coordinates on a Number Line.