The length of VX equals to 80
Below I show my work of how I found the missing length.
To find the missing length, you pick the starting location. Then go in any direction and then do the same to the other side. Then write a ratio.
I decided to start at 46 and then go downward.
46/23=x/17
Then you cross multiply
43*17=x*23
782=23x
Divide 23 on both sides
X=34.
Then add 34 by 46 to get the length of VX.
Below is a picture of notes on how to solve these types of problems.