Simon is riding a bike at 12 km/h away from his friend Keesha. He throws a ball at 5 km/h back to Keesha, who is standing still on a sidewalk.

The ball’s 5 km/h speed is relative to Simon, who is moving away from Keesha at 12 km/h. Since he throws it backward, subtract the ball’s speed from the bike’s speed: 12 − 5 = 7 km/h. The ball therefore moves away from Keesha at 7 km/h relative to the sidewalk, so the correct choice is 7 km/h.

AI-written and checked against the verified answer.