Two astronauts push off of each other in space. the 80kg astronaut ends up going 10 m/s. the other one ends up going 8 m/s. what is the mass on the other astronaut?

We have to use conservation of momentum here.
So m1*v1=m2*v2
where m1 and m2 are masses and v1 and v2 are velocitis
We can easily tranform our formula to get m2

Now we can substitute our data
m2= [kg] - its our result