Please help me answer this question. Please have answer in grams with correct significant figures.
A ball of mass 20.0g collides with another ball of unknown mass at rest. The collision is elastic (kinetic energy is constant), and after impact the 20.0-g ball travels away at a 55.6o angle from its original direction, and the other ball travels away at a - 50.0o angle. What is the mass of the other ball in grams and using correct significant figures?