Final answer:
The direction of the net force on charge 3 can be determined using the left-hand rule for magnetic forces.
Step-by-step explanation:
The direction of the net force acting on charge 3 can be determined by applying the left-hand rule for magnetic forces. To find the direction, place your left hand so that your fingers point in the direction of the velocity of charge 3 and curl them upward toward the magnetic field. The net force on charge 3 is in the direction in which your thumb points.
In this case, if charge 3 is positive, the net force will act in a direction perpendicular to both the velocity and the magnetic field. If charge 3 is negative, the net force will act in the opposite direction.
Therefore, to answer the question, we need more information about the velocity and magnetic field in relation to charge 3.