Answer:
0.76 = 76% probability that he will wait longer than 6 minutes
Explanation:
A distribution is called uniform if each outcome has the same probability of happening.
The uniform distribution has two bounds, a and b, and the probability of finding a value higher than x is given by:

A geyser erupts every 25 minutes. A hiker has not consulted a schedule before heading to see the geyser, so the amount of time he spends waiting to see an eruption follows a uniform distribution.
This means that

What is the probability that he will wait longer than 6 minutes?

0.76 = 76% probability that he will wait longer than 6 minutes