I cant answer Question of Fifteen stick man HELP
Five row over, one has to row back (4), they have four more enter the boat and row to the island, but one has to row it back (4), four more enter the boat and they row to the island, but time runs out and the five on board are safe on the island (5). So, it is 4+4+5=13.
May the Godesses have mercy on the souls of the two left behind!