[tex]\displaystyle\bf\\\begin{vmatrix}\bf2x+1 &\bf x\\\bf5&\bf-3 \end{vmatrix}=0\\\\\\-3(2x+1)-5x=0\\\\-6x-3-5x=0\\\\-6x-5x=3\\\\-11x=3\\\\x=\frac{3}{-11}\\\\\boxed{\bf x=-\frac{3}{11}}[/tex]
