\(\sum_{i=1}^n (x_i - 3) = 0\) Or, \(\sum_{i=1}^n x_i - \sum_{i=1}^n 3 = 0\) Or, \(\sum_{i=1}^n x_i - 3n = 0\) ——— (i) \(\sum_{i=1}^n (x_i + 3) = 66\) Or, \(\sum_{i=1}^n x_i + \sum_{i=1}^n 3 = 66\) Or, \(\sum_{i=1}^n x_i + 3n = 66\) ——— (ii) Subtracting equation (i) from equation (ii), we get: \(6n = 66\) Or, \(n = 11\) Substituting \(n = 11\) into equation (i), we get: \(\sum_{i=1}^n x_i - 3 \times 11 = 0\) Or, \(\sum_{i=1}^n x_i = 33\) Therefore, \(\bar{x} = \frac{\sum_{i=1}^n x_i}{n} = \frac{33}{11} = 3\) Hence, \(\bar{x} = 3\) and \(n = 11\)