a, \(-1,8:\left(1-\frac{3}{4}\right)\)
\(=-\frac{9}{5}:\frac{1}{4}\)
\(=-\frac{36}{5}\)
b, \(\left(\frac{7}{8}-\frac{3}{4}\right)\cdot1\frac{1}{3}-\frac{2}{7}\cdot\left(3,5\right)^2\)
\(=\left(\frac{7}{8}-\frac{6}{8}\right)\cdot\frac{4}{3}-\frac{2}{7}\cdot12.25\)
\(=\frac{1}{8}\cdot\frac{4}{3}-\frac{2}{7}\cdot\frac{49}{4}\)
\(=\frac{1}{6}-\frac{7}{2}\)
\(=\frac{1}{6}-\frac{21}{6}\)
\(=-\frac{20}{6}\)
\(=-\frac{10}{3}\)