Question 648731
Hi.  You want to find out how many ways that a student can take one of each class.  So 9 psychology classes, four history, thirteen math, and five business courses.
To find the answer, you need to multiply all the numbers of a certain course there are available.  In this case: 9*5*13*5=2925 ways.

To relate this to another problem:

Lets say that you want to make a sandwich.  You have four meats, 2 kinds of bread, and 3 kinds of cheese.  How many different sandwiches can you make with what you have.  This problem is similar to the other problem, since you want to find the different possibilities of classes to take.  The answer to this example is 4*2*3 or 24.