.
            You do not understand the meaning of the problem.
The problem says that the height of waves is UNIFORMULY DISTRIBUTED between the marks 1 ft and 9 ft.
Then they ask 
(a)  What is the probability that the waves will less than 2 feet in height ?
        Less than 2 feet means that it is between 1 ft and 2 ft.
        Comparing the length of this interval [1 ft, 2 ft], which is 2-1 = 1 ft,
        with the total possible interval from 1 ft to 9 ft,
        we see that the probability is  
.
(b)  In this case, the observation is between 4 ft and 6 ft: the length of the 
     interval is 6-4 = 2 ft
      Comparing it with the total possible interval from 1 ft to 9 ft, 
      we see that the probability of such observation is  
 = 
 .    ANSWER
Solved and explained,  patiently and carefully.