Explanation:
Torque = Force * Perpendicular distance of the force = 10N * 0.8m = 8Nm.
In diagram A, both torques are acting in a clockwise direction. Hence the net torque is 2N * 1m + 4N * 1m = 6Nm, clockwise.
In diagram B, the torques are acting in opposite directions. For the clockwise one, its torque is 5N * 4m = 20Nm. For the anticlockwise one, its torque is 2N * 10m = 20Nm. Since they are in opposite directions and are equal, they cancel out each other.
Hence net force = 0N and net torque = 0Nm.
