Dear experts solve this is x=-14? Pl solve

3. Find x such that $\left[1 x 1\right] \left[\begin{array}{ccc}1& 3& 2\\ 2& 5& 1\\ 15& 3& 2\end{array}\right]\left[\begin{array}{c}1\\ 2\\ x\end{array}\right] = 0$