You have 5 shirts, 4 pants and 6 shoes how many outfits can you make

Multiply out the values: 5*4*6 = 20*6 = 120

If we have 5 shirts and 4 pants (ignore the shoes for now), then there are 5*4 = 20 different outfits to choose from. Imagine there's a 5 by 4 table. The 5 rows represent the number of shirts, while the 4 columns is the number of pants. The 20 cells in the middle is each combo

For each combo of shirts+pants, you pick a pair of shoes. So we have a new 20 by 6 table. The 20 rows represents the shirts+pants combo (from the older table) while the 6 columns is the number of shoes. There will be 20*6 = 120 cells in this second table.