Average speed = Total distance ÷ Total time.<br><br>&bull; First leg: 9 km at 3 km/h → time = 9 ÷ 3 = 3 h.<br>&bull; Second leg: 6 km at 6 km/h → time = 6 ÷ 6 = 1 h.<br>&bull; Total distance = 9 + 6 = 15 km.<br>&bull; Total time = 3 + 1 = 4 h.<br>&bull; Average speed = 15 ÷ 4 = 3.75 km/h.<br><br>Final Answer: 3.75 km/h