The overall momentum of the system is conserved before and after collision.
Before the collision:
Momentum = 3.00*2.09 - 2.22*3.92 = -2.4324 (keep in mind that the motions are opposite in directions so they are supposed to have opposite signs. I chose leftward motion as negative and rightward motion as positive)
After the collision:
<h3>Momentum = -3.00*1.71 + 2.22*x;</h3>
Since momentum is conserved:
<h3>-3.00*1.71 +2.22x = -2.4324</h3>
Solve for x to find the velocity of the 2nd block.