Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

A billiard ball moving at 6.00 m/s undergoes an elastic collision with another billiard ball having the same mass.  After the collision, the first billiard ball moves at 4.25 m/s at an angle of 35o with respect to the original line of motion.  Find the velocity, in m/s, of the other billiard ball after the collision.  In addition, show that the collision is elastic.

help!!!