Five point charges, each of value + q are placed on five vertices of a regular hexagon of side L. What is the magnitude of the force on a point charge

Among the five forces on five charges,2 pairs (four) of forces cancel with each other since they are equal in magnitude and opposite in direction.

The resultant force is due to a single force given below.

F = q² / 4 π ε₀ L²

The magnitude of the force on a point charge of value - q placed at the centre of the hexagon is

F = q² / 4 π ε₀ L²