Pizza house offers 4 different​ salads, 4 different kinds of​ pizza, and 5 different desserts. how many different three course meals can be​ ordered

To find out how many 3 course meals there are you will multiply all three numbers together.  The reason for this is that you can group each item with each of the other options.  This is a triple grouping.

4 x 4 x 5 = 80

There are 80 possible combinations.