This should be a simple a problem. All you have to do is set up a triangle.
The truck travels 21 blocks north and 26 blocks south, that means that the truck travels 5blocks south:
21 blocks north+26 blocks south= -5 block north=5 blocks south
The truck travels 17 east.
Now set up a triangle,
The triangle will have a height of 5and base of 17.
To find the magnitude of displacement, use the pythag.
5^2+17^2=c^2
= 17.72
So the truck is17.72blocks away from the starting point.
Now to find the direction, you will need to use basic trig:
so tanx=height/base, x=tan-1(height/base)=tan-1(5/17)=-3.30
Remember that the net travel was in the south direction, therefore the direction will be -3.30degrees.
