The astronaut final velocity is 0.06 m/s to the right
Explanation:
In absence of external forces, the total momentum of the box-astronaut system is conserved.
At the beginnig, the total momentum of the two is zero, since they are at rest:

While the final momentum, after the astronaut throws the box, is:

where
m = 11 kg is the mass of the box
M = 79 kg is the mass of the astronaut
v = -0.45 m/s (to the left) is the velocity of the box (we take left as negative direction)
V is the final velocity of the astronaut
The total momentum is conserved, so

And solving , we find V:

And the positive sign indicates that the direction is to the right.
Learn more about momentum:
brainly.com/question/7973509
brainly.com/question/6573742
brainly.com/question/2370982
brainly.com/question/9484203
#LearnwithBrainly