Advanced permutation/combination problems combine multiple concepts and constraints. Multi-stage selection: Apply counting principle with C/P at each stage. Example: Select 2 committees from 10 people (3 from committee A, 2 from B) = C(10,3) × C(7,2). Constraint handling: At least/at most conditions use complementary counting. Distribution with constraints: Distributing 12 items into 3 boxes with each box getting at least 2 = distributing 6 remaining items freely = C(6+3-1, 3-1) = C(8,2). Shortcut: Visualize using diagrams, organize constraints systematically. Exam tip: Practice multi-constraint problems. Verify using simple cases. Show all working.