What is the mean deviation of first 10 even natural numbers?

If $\rm \displaystyle \sum_{i = 1}^{10}x_i = 110$ and $\rm \displaystyle \sum_{i = 1}^{10}x_i^2 = 1540$  then what is the variance?

If M is the mean of n observations x₁ - k, x₂ - k, x₃ - k, _ _ _, x_n - k, where k is any real number, then what is the mean of x₁, x₂, x₃, _ _ _, x_n?

What is the sum of deviations of the variate values 73, 85, 92, 105, 120 from their mean?