A cart of 2kg travellin @6m/s collides wit another cart of mass of 0.4kg travellin in the same direction @ 2m/s. The 2kg cart bounc off and cöntinues wt 3m/s in the same direction after impact.calculate the velocity of the 0.4kg trolley afta collision

Apply the law of conservation of linear momentum. There wil be only one unknown