Answer:
1.22 m/s (or 1 m/s if you use sig figs)
Explanation:
Our equation is m1v1+m2v2=m1v1+m2v2
Plug in our numbers to get:
3(2.09)+2.22(-3.92)=3(-1.71)+2.22(vf)
Then solve. We can simplify by doing:
6.27-8.7024=-5.13+2.22(vf)
Then combine the left side
-2.4324=-5.13+2.22(vf)
Add 5.13 to both sides
2.6976=2.22(vf)
Divide by 2.22
vf=1.22 m/s (or 1 m/s with sig figs)
Hope this helps