[tex] \frac{-7}{10} : \frac{14}{15} - \frac{-1}{30} *2 \frac{1}{2} =\\\\
\frac{-7}{10} : \frac{14}{15} - \frac{-1}{30} * \frac{2*2+1}{2} =\\\\
\frac{-7}{10} : \frac{14}{15} - \frac{-1}{30} * \frac{5}{2}=\\\\
\frac{-3}{4} - \frac{-1}{12}= \\\\
\frac{-3*3}{4*3} - \frac{-1}{12} =\\\\
\frac{-9}{12} - \frac{-1}{12} =\\\\
\frac{-8}{12} [/tex]