During a certain chess tournament, each of six players will play with every other player exactly once. Then, how many different matches will be played during the tournament?

During a certain chess tournament, each of six players will play with every other player exactly once. Then, how many different matches will be played during the tournament?

• 12 (Incorrect)
• 15 (Correct)
• 18 (Incorrect)
• 30 (Incorrect)