Final answer:
Starting at -7, walking 8m in the negative direction results in a position of -15. Then, walking 20m in the positive direction leads to a final position of 5. Hence, the displacement is 12m.
Step-by-step explanation:
If a person starts out at -7 and walks 8 meters in the negative direction, their position would change to -7 - 8 = -15. Then, if they turn around and walk 20 meters in the positive direction, their position would change to -15 + 20 = 5. The displacement of the person is the change in position, which is the final position minus the initial position. Thus, the displacement is 5 - (-7) = 12 meters.
The correct answer is c. 12m.