Since Astronaut and wrench system is isolated in the space and there is no external force on it
So here momentum of the system will remain conserved
so here we can say

initially both are at rest
so here plug in all values


so here the astronaut will move in opposite direction and its speed will be equal to 0.20 m/s
X=15! hope this helps! Also please look at my questions about the cannon ball!!! need help!
Answer:
Part a)

Part b)

Explanation:
Part a)
As we know that the target is at distance 75 m from the hunter position
so here we will have

here we know that

so we have


now in the same time bullet will go vertically downwards by distance



Part b)
In order to hit the target at same level we need to shot at such angle that the range will be 75 m
so here we have


