А)
$$ - \frac{7}{5} - \frac{3}{10}=-( \frac{14}{10}+ \frac{3}{10})= -\frac{17}{10}=-1 \frac{7}{10}=-1,7 $$
б)
$$ -\frac{5}{6} + \frac{3}{8} = \frac{3}{8} -\frac{5}{6}= \frac{9}{24}-\frac{20}{24} =- \frac{11}{24} $$
в)
$$ - \frac{8}{25} *\frac{15}{18} = -\frac{8*15}{25*18}=- \frac{4*3}{5*9}=- \frac{4}{5*3}=- \frac{4}{15} $$
г)
$$ -7: (-\frac{14}{9}) =-(7+ \frac{9}{14})=-7 \frac{9}{14} $$