[gregw134]

Yeah 3.5 still can't figure it out, 4 does though. Hilariously 3.5 gave me this:

Fill the 6-liter jug completely with water. Pour the water from the 6-liter jug into the 12-liter jug. Fill the 6-liter jug again with water. Pour water from the 6-liter jug into the 12-liter jug until the 12-liter jug is full. This leaves 4 liters of water in the 6-liter jug. Empty the 12-liter jug. Pour the 4 liters of water from the 6-liter jug into the empty 12-liter jug. Fill the 6-liter jug with water again. Pour water from the 6-liter jug into the 12-liter jug until the 12-liter jug is full. This leaves exactly 6 liters of water in the 12-liter jug.