A flag is made of three horizontal strips of fabric, each of a solid color, either red, white, blue or green. If no two adjacent strips can be the same color, how many distinct flags are possible?
You have four choices for the bottom strip.
You have three choices for the middle strip (every color but the bottom strip).
You have three choices for the top strip (every color but the middle strip).
4 x 3 x 3 = 36 flags