Solve the following system of equations.

$\displaystyle

x_1-x_2+x_3=-5

$

$\displaystyle

3x_1+x_2-x_3=25

$

$\displaystyle

2x_1+x_2+3x_3=20

$

$\displaystyle

6x_1+x_2+3x_3=40

$

Does this system has a unique solution or infinitely many solutions? Justify your answer.

please explain to me how to do it, thank you!