\[1\frac{1}{8}\ :\left( - 3\frac{3}{4} \right) = - \frac{9}{8}\ :\frac{15}{4} =\]
\[= - \frac{9}{8} \cdot \frac{4}{15} = - \frac{3}{2 \cdot 5} =\]
\[= - \frac{3}{10} = - 0,3.\]