The series has two interleaved patterns: Positions 1,3,5,7: 5, 24, 2, ? and Positions 2,4,6: 20, 6, 8. Looking at adjacent pairs: (5,20), (24,6), (2,8), each pair shows x × 4 = next. Following this pattern, ? × 4 = 12 (from position 8?), so ? = 12. Alternatively, pattern 5→20 is ×4, 20→24 is +4, 24→6 is ÷4, 6→2 is -4, 2→8 is ×4, so 8→12 is +4, continuing the cycle ×4,+4,÷4,-4.