\[0,3a = 0\]
\[a = 0.\]
\[0,3a = 0,6\]
\[a = 0,6\ :0,3\]
\[a = 2.\]
\[03a = - 0,8:\]
\[a = - \frac{4}{5}\ :\frac{3}{10} = - \frac{4 \cdot 10}{5 \cdot 3} =\]
\[= - \frac{40}{15} = - 2\frac{2}{3}.\]
\[0,3a = - 1:\]
\[\ a = - 1\ :0,3 = - 1\ :\frac{3}{10} =\]
\[= - \frac{10}{3} = - 3\frac{1}{3}.\]