To solve this problem you must apply the proccedure shown below:
 1. You have that the line segment has the following endpoints: (-14,-5) and (-14,15).
 2. As you can see, the x coordinates of both point are the same, so, the line segment is vertical and goes from 15 to -5 , therefore, you can calculate the length as following:
 L=15-(-5)
 L=15+5
 L=20
 Therefore, as you can see, the answer is: 20