A 5.00g object moving to the right with a speed of 20.0cm/s makes an elastic head-on collision with a 10.0g object initially at rest. Find:

1. The velocity of each object after the collision.

2. The fraction of the initial energy transferred to the 10.0g object.

So for part one I used the elastic and conservation formula, I subtracted the equations to solve for v1f and decided to add them for v2f but the answer Im getting doesnt seem correct.