A charged particle moving in a magnetic field has a force to the top of the page when it is moving toward the right and the field is into the page. Is this particle positive, negative or neutral?

Use the right-hand rule to find the direction of the magnetic force on a positive charge. Point your fingers in the direction of the velocity (right), and curl them toward the direction of the magnetic field (into the page). Your thumb will point in the direction of the force.

Observe that your thumb points to the top of the page, which matches the given direction of the force on the particle.