If you're using a TI-83, it's a little less straightforward than with the later versions because, unlike the 83, they bring up a screen that shows you exactly where to put each bit of information.
The keystrokes are 2ND VARS (DISTR), then select normcdf. Then the order things go is (lower, upper, mean, sd).
For lower, we need the closest we can get to negative infinity, which is -1E99. The E (which is scientific notation) can be produced by doing 2ND , (comma).
Upper is, of course, 75. Then the mean is exactly what the problem says, which is 76.
The standard deviation of 16 changes based on the sample size of 38. In this spot, we put 16/√38.
Once all that is in, your calculator will give you the result of 0.3500.
