An object travels North at #9 m/s# for #4 s# and then travels South at #3 m/s# for # 1 s#. What are the object's average speed and velocity?
While going North, the object goes
While going South, the object goes
For average speed , direction does not matter, just total distance and total time.
For average velocity, direction does matter, so we need the resultant of all displacements (which are vectors) and total time.
I hope this helps,