9000019907

The augmented matrix of a system of three equations with three unknowns is row equivalent with the following matrix $A^{\prime }$. Find the solution of the system. $$A^{\prime }=\left(\begin{array}{cccc}1& 2& 4& 0\\ 0& 2& 7& 7\\ 0& 0& 7& 35\end{array}\right)$$