TeX source:
\begin{array}{rclcll}\mathbb{D} &=& \mathbb{R} \cr\cr 0 &=& 3^x-2 &\vert& -3^x \\-3^x &=& -2 &\vert&\cdot (-1) \\3^x &=& 2 &\vert& \log_{3}() \\x &=& \log_{3}(2)\end{array}