Final answer:
To determine who won the race and by how many seconds, calculate the time it took for each runner to reach the 100-meter mark. Compare the times to determine the winner.
Step-by-step explanation:
To determine who won the race and by how many seconds, we need to calculate the time it took for each runner to reach the 100-meter mark.
Since Emily gave John a 10-meter head start, we can consider John's run as a 90-meter race. Let's assume both Emily and John ran at a constant speed.
Based on the given information, we can calculate the time it took for John to reach the 100-meter mark:
John's time = (100 m - 90 m) / John's speed
Once we have John's time, we can determine Emily's time:
Emily's time = John's time + 10 seconds
Comparing Emily's and John's times will help us determine who won the race and by how many seconds.