The following test scores were recorded for a student: 89, 81, 77, 77, 89, 91. find the mean, median, and mode

Mean: We add them all and divide by the number of them:  = 84
Median: We put them in order and take halfway inbetween the two middle values: 77, 77, 81, 89, 89, 91.  = 85
Mode: We find the most common value. In this case both 77 and 89 appear twice, so 77 and 89.

Is there more to the question?