## Algebra 2 (1st Edition)

From the exercise $\overline{x}=\frac{x_1+x_2+...+x_n}{n}$. Then $\frac{ax_1+ax_2+...+ax_n}{n}=\frac{a(x_1+x_2+...+x_n)}{n}=a\frac{x_1+x_2+...+x_n}{n}=a\overline{x}$ Thus we proved what we had to.