The reduced row echelon form of a system of linear equations is given. Write the system of equations corresponding to the given matrix. Use $x, y ;$ or $x_{1}, x_{2}, x_{3}, x_{4}$ as variables. Determine whether the consistem or inconsistent. If it is consistent, give the solution.
$$
\left[\begin{array}{lll|r}
{1} & {0} & {0} & {0} \\
{0} & {1} & {0} & {0} \\
{0} & {0} & {0} & {2}
\end{array}\right]
$$