\[\frac{1}{3x} = \frac{0,5}{0,3}\]
\[3x = \frac{1 \cdot 0,3}{0,5} = \frac{3}{5}\]
\[x = \frac{3 \cdot 1}{5 \cdot 3} = \frac{1}{5} = 0,2.\]
\[Ответ:x = 0,2.\]