Step-by-step explanation:
The given data is as follows.
Velocity of truck = 12 m/s
The turtle has moved in 18 m towards south direction. After that, the truck picks up the turtle towards 1100 m north.
Hence, total displacement will be as follows.
1100 m - 18 m = 1082 m in the north direction
Time taken by the turtle is 3.5 minutes. Converting time into seconds as follows.

= 210 sec
And, the time taken by the truck is as follows.
= 91.67 sec
Therefore, the total time will be calculated as follows.
210 sec + 91.67 sec
= 301.67 sec
Now, we will calculate the average velocity as follows.
Average velocity =

=
m/s
= 3.586 m/s
Thus, we can conclude that average velocity of the turtle for its entire journey is 3.586 m/s.