A student was asked to find the value of x, and given the arithmetic mean is 12 of the following 12 numbers: 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and x

5 7 8 11

7

Mean = \(\frac{sum \; of \; observations}{number \; of \; observations}\) Given mean = 12 Mean = \(\frac{3 + 11 + 7 + 9 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + x}{12}\) = 12 137 + x = 12 × 12 x = 7