7). The displacement is how far away from the starting point the object ends up being. Since the person is running a lap, they should end up at the same place they started.
The distance is given in the problem, so:
a). 600
b). 0
8). To find the distance, calculate the perimeter. Since the book ends up at the original location, the displacement is zero, so
a). 0
b). 14
Using the same strategy:
9a. 150 - 75 = 75
9b. 150 + 75 = 225
9c. 150 + 75 = 225 both times
10a. 14 + 7 + 2 = 23
10b. 14 - 7 + 2 = 9
11a. 10 + 4 + 2 = 16
11b. 10 - 4 + 2 = 8