Displacement is change in position over time. Their change in position is 0. Their final position is the exact same as their initial (where they started).
Average speed is total distance, not displacement. They ran 16 kilometers and back another 16 kilometers. That’s 32 kilometers. We want to change this into meters tho. That’s the si unit for speed. So multiply that by 1000 to get 32,000 meters. Now divide that by the time. Again, convert that hour and 15 minutes into seconds because the si unit for time is seconds. Do 1*3600 and then add 15*60 to get 4,500 seconds.
32,000m/4,500s = 7.1 m/s
Average velocity is displacement over time. We already went over that the displacement is 0, so therefore average velocity is 0