Multiple choice general knowledge math & puzzles 55, 34, 21, 13 ... 12 8 4 11 Reveal answer Fill a bubble to check yourself B Correct answer Explanation This is the Fibonacci sequence in reverse: 55, 34, 21, 13... Each number is the sum of the two preceding it in the standard sequence (8+13=21, 13+21=34, etc.). Therefore, the number before 13 is 8 (21 - 13 = 8).