\[\frac{1}{3}x - 2x = \left( \frac{1}{3} - 2 \right)x =\]
\[= \left( \frac{2}{6} - \frac{12}{6} \right)x = - \frac{10}{6}x =\]
\[= - \frac{5}{3}x = - 1\frac{2}{3}x\]