Answer: 22 units.
Step-by-step explanation:
Here FSB and ZDR are two triangles.
In which, FS = 38 unit, FB = 55 unit, ZD = 15.2 unit and ZR = x unit.
Also, 
Thus, By the property of similarity,

⇒ 
⇒ 
⇒ 
⇒
Thus, ZR = 22 unit.
It would be 0 because as you go along it doesn't go up but keeps moving. An undefined slope is up and down/vertical.