identify mass, velocity, and more

Question

Ball A, with a mass of 20 kilograms, is moving to the right at 20 meters per
second. At what velocity should ball B, with a mass of 40 kilograms, move so
they both come to a standstill upon collision? Identify each mass, velocity,
and unknown. Show your work, including units, and indicate the direction of
ball B in your answer.

Answer 1

P_1+P_2=0