Hi all, I'm practicing for a mid-semester linear algebra exam and I'm stuck on this question:

Let Ax=bwhere A = $\displaystyle \begin{bmatrix} 2 & 1 & 0 \\ -3 & 0 & 1\\ 0 & 1 & 2 \end{bmatrix}$ , det A = 4 andb= $\displaystyle \begin{bmatrix} 7 \\ -8 \\ -3 \end{bmatrix}$. What does x2 equal?

I know I could just use row reduction to solve for x2 but I would like to know how to use the determinant to make the problem easier.

Thanks,