Variance of a Linear Combination of Variables

Let X, Y, and Z be random variables with the following means and standard deviations: $\mu_X = 10, \sigma_X = 2$; $\mu_Y = 15, \sigma_Y = 3$; and $\mu_Z = 20, \sigma_Z = 4$. The correlation between any pair of these variables is $\rho = 0.5$. What is the value of $\mathrm{Var}(X + Y - 2Z)$?