If a tennis ball and a bowling ball collide in midair, does each undergo the same amount of momentum change?

Answer 1

Momentum is conserved so the net change in momentum is zero and with only two bodies find the difference between the before and after momentum for system and arrange terms
M(V1-V2)= -m(v1-v2)

Answer 2

What assumptions do you want to make about the collision? I don't think I could assume an inelastic collision between the two, which would complicate the calculations ..