Statement - I : The relative velocity between any two bodies moving in opposite direction is equal to sum of the velocities of two bodies.
Statement - II : Sometimes relative velocity between two bodies is equal to difference in velocities of the two bodies. 

The relative velocity between two bodies is equal to the total of the velocities of the bodies when they are travelling in the opposing directions. Yet, if both bodies are travelling in the same direction, their relative velocities are equal to their individual velocities.