find the mean median and mode for the data set:

15,16,21,23,25,25,25,39

Mean: (15+16+21+23+25+25+25+39)/8 = 23.5

Median: the midpoint of the ordered data is 24 (the fourth and fifth values), so the median is 24.
Mode: The mode is 25, since it occurs more frequently than any other value.