The first option and the third option are correct.
(Although, it's probably way too late now...)
Answer:
13.187 meters
Step-by-step explanation:
Basically, there are 24 meters for every 91 steps: 
There are x meters for every 50 steps: 

Cross multiply
91x = 1200
Divide both sides by 91 to isolate the variable, x
91x/91 = 1200/91
x = 13.186813
What exactly is it you need help with?