TeX Quellcode:

\begin{array}{rclcll}\dfrac{12-x}{4x-8} &\leq & 1 &\vert & \cdot\left(4x-8\right) \\12-x &\leq & 4x-8 &\vert & +8+x \\20 &\leq & 5x &\vert & :5 \\4 &\leq & x \\x &\geq& 4\end{array}