Can I get help and an explanation on C?

Answer:
1.67 m/s
Explanation:
Momentum is conserved.
Initial momentum = final momentum
(30 kg) (10 m/s) + (35 kg) (-10 m/s) = (30 kg) v + (35 kg) (0 m/s)
300 - 350 = 30v
v = -5/3 m/s
Linus will move at 1.67 m/s in the direction opposite that he started.