How do i do problems like this? " the time required to finish a test is normally distributed with a mean of 60 minutes and a standard deviation of 10 minutes. what is the probability a student will finish the test between 50 and 60 minutes?"

Let the time taken to finish the test be x.

P (50 < x < 60) = P (x < 60) - P (x < 50) = P (z < (60 - 60) / 10) - P (z < (50 - 60) / 10) = P (z < 0) - P (z < - 1) = P (z < 0) - (1 - P (z < 1)) = P (z < 0) + P (z < 1) - 1 = 0.5 + 0.8413 - 1 = 0.3413