Average velocity is defined as the ratio of displacement and time
where displacement is straight line distance between initial point and final point
here we know that object moves in straight line towards North by 80 m
time taken = 4 s
now using the formula
[tex]velocity = \frac{displacement}{time}[/tex]
[tex]v = \frac{80}{4}[/tex]
[tex]v = 20 m/s[/tex]
So the velocity of this motion is 20 m/s towards North