I need help with these problems.

Two girls with masses of 50.0 kg and 70.0 kg are at rest on frictionless in-line skates. The larger girl pushes the smaller girl so that she rolls away with a speed of 10.0 m/s. What is the velocity of the larger girl? Type of Collision : Answer (in full sentence): 5. A raft of mass 180 kg carries two swimmers of mass 50 kg and 80 kg. The raft is initially at rest. The two swimmers simultaneously dive off opposite ends of the raft, each with a horizontal speed of 3.0 m/s. With what speed and in what direction does the raft start to move? Hint: You'll want to add another row to your chart since there are now three objects instead of two. Type of Collision : Answer (in full sentence): 6. In a freight yard a train is being put together from freight cars. An empty freight car, coasting at 10 m/s, strikes a loaded car that is stationary, and the cars couple together. Each of the cars has a mass of 3,000 kg when empty, and the loaded car contains 5,000 kg of salad and apples. With what speed does the combination of the two cars start to move? Type of Collision : Answer (in full sentence)