With displacement, all we care about is the beginning and end. We don't care about the middle part(s) of the journey. So we'll take the straight line route from beginning to end when it comes to computing displacement.
We start at A(0,0) and end at B(-2,0). Going from A directly to B has us go 2 km west. Keep in mind that displacement is a vector, so you must include the direction along with the distance.
