I'm not sure how to do this one, I row reduced a bit but don't know where to go with it.

$\displaystyle

\begin{bmatrix}

1 & 2 & 2 & | & 1 \\

2 & 1 & 3 & | & 3 \\

4 & 5 & 7 & | & \lambda \\

\end{bmatrix}

$

How do I find the value of $\displaystyle \lambda$ for which the equations are consistent?

Thanks