In a mathematics class, the teacher recorded the scores of 20 students on a recent exam. The scores are as follows:
82, 75, 88, 91, 67, 39, 70, 97, 85, 60, 94, 73, 55, 78, 92, 76, 80, 85, 90, 82
To analyze the performance of the class, the teacher calculated the mean score. What is the mean of these scores?