The mean deviation of the data 3, 10, 10, 4, 7, 10, 5 from mean is :

Mean = (3 + 10 + 10 + 4 + 7 + 10 + 5)/7 = 49/7 = 7. The absolute deviations from 7 are 4, 3, 3, 3, 0, 3, 2, which add to 18. Mean deviation = 18/7.