TeX source:
\begin{array}{rclcl} \mathbb{D} &=& \mathbb{R} \cr\cr \dfrac{1.000^{x+1}}{10^{5x}}-12 &=& 43 &\vert& \text{5. Potenzgesetz} \cr\cr \dfrac{\left(10^3\right)^{x+1}}{10^{5x}}-12 &=& 43 &\vert& \text{2. Potenzgesetz} \cr\cr 10^{3x+3-5x}-12 &=& 43 &\vert& +12 \cr 10^{-2x+3} &=& 55 &\vert& \lg() \cr -2x+3 &=& \lg(55) &\vert& -3 \cr -2x &=& \lg(55)-3 &\vert& :(-2) \cr x &=& \dfrac{\lg(55)-3}{-2} \approx 0{,}63 \cr\cr \mathbb{L}&=&\left\{\dfrac{\lg(55)-3}{-2}\right\} \end{array}