Answer:
0.1 = 10% probability that the class length is between 51.5 and 51.7 min, that is, P(51.5 < X < 51.7) = 0.1.
Step-by-step explanation:
A distribution is called uniform if each outcome has the same probability of happening.
The uniform distributon has two bounds, a and b, and the probability of finding a value between c and d is given by:

The lengths of a professor's classes has a continuous uniform distribution between 50.0 min and 52.0 min.
This means that 
If one such class is randomly selected, find the probability that the class length is between 51.5 and 51.7 min.

0.1 = 10% probability that the class length is between 51.5 and 51.7 min, that is, P(51.5 < X < 51.7) = 0.1.