A person needs to walk two flat slopes with equal distances from point A to point B, one uphill and one slope (the distance of uphill and downhill is equal), the speed of flat slope is 4km/hour, the speed of uphill is 3km/hour, and the speed of downhill is 6km/hour I walked for 6 hours in total, how many kilometers is a flat slope and an uphill?
一人从A地走到B地要走两个路程相等的平坡、一上坡、一个坡(上下坡路程相等)，平坡速度4km一小时、上坡速度3km一小时、下坡速度6km一小时共走了6小时问一个平坡和一个上坡多少km？
<result>12</result>