TeX source:
\begin{array}{rclcl}0 &=& \sqrt[2]{\sqrt[2]{49^{\frac{1}{2}}\cdot x}\cdot 19}\\0 &=& \sqrt[4]{7x}\cdot\sqrt{19} &\vert& :\sqrt{19}\\0 &=& \sqrt[4]{7x} &\vert& ()^4\\ 0 &=& 7x &\vert& :7\\0 &=& x \in \mathbb{D} \end{array}