For which of these data sets are the mean, the median and the mode all equal?

For 3, 5, 5, 5, 7 the total is 25, so the mean is 5; the middle of the five ordered values is 5; and 5 occurs three times, more than any other value. All three averages agree. The set 2, 4, 6, 8, 10 has mean and median both 6 but no value repeats, so it has no mode to compare. The set 1, 2, 2, 3, 7 has mean 3, median 2 and mode 2, so the single large value 7 pushes the mean above the other two. And 4, 4, 6, 8, 8 has mean and median 6 but two modes, 4 and 8, neither equal to 6.