Let’s see, you have three missionaries and three cannibals, and one canoe that holds two people. Send two cannibals across, send one back with the canoe. Then send two missionaries across, and....oops.
You have one canoe holding three missionaries, and another canoe holding three cannibals; the first canoe leaves New Orleans going upstream at 6 mph; the second canoe leaves Cairo Illinois going downstream at 10 mph...