Given the augmented matrix below, solve the associated system of equations.

{[1 6 −9 −4 7 −3 −4], [0 0 0 0 1 −5 −9], [0 0 0 0 0 1 −7]}

For the variables, use x₁,x₂,x₃,x₄,x₅, and x₆.