15. (15 points) There are 8 football teams participating in a round-robin tournament. The winning team gets 1 point, the losing team gets 0 points, and in the case of a draw, both teams get 0.5 points. After the tournament, the teams are ranked based on their points from highest to lowest, and it is found that: all teams have different scores, and the second-place team's score is the same as the total score of the last four teams. Find the score of the team that finished in second place.
【Answer】Solution: Each team needs to play 7 matches, so a team that wins all matches gets 7 points,
while the last four teams playing 6 matches among themselves will score at least 6 points in total,
thus the second-place team must score at least 6 points.
If the first-place team wins all matches, then the second-place team only loses to the first-place team, scoring 6 points;
If the second-place team scores 6.5 points, then the second-place team has 6 wins and 1 draw, the first-place team can at best also have 6 wins and 1 draw, which contradicts the condition that all scores are different.

Therefore, the second-place team scores 6 points.
Answer: The second-place team scores 6 points.