Answer:
24 kg m/s
Step-by-step explanation:
The change in momentum of the wrench is given by:

where
is its final momentum
is its initial momentum
At the beginning, the wrench is at rest together with the astronaut, so its momentum is zero:

After it is launched, its momentum becomes

where
m = 2.0 kg is its mass
v = 12 m/s is its velocity (taking the direction of the wrench motion as positive)
Substituting,

So, the wrench's change in momentum is
