Вычислите: а) (−50/99) · 11/25; б) (−2 2/3) : (−0,08); −1,34 + 1/40 : (−2 11/12); 4/5 + (−2,8) · (2 1/3 : 2,8 − 1).

а) \(\left(-\frac{50}{99}\right)\cdot\frac{11}{25}=-\frac{2}{9}\).

б) \(\left(-2\frac{2}{3}\right):(-0,08)=-\frac{8}{3}:-\frac{2}{25}=-\frac{8}{3}\cdot\left(-\frac{25}{2}\right)=\frac{100}{3}=33\frac{1}{3}\).

\(-1,34+\frac{1}{40}:(-2\frac{11}{12})=-\frac{67}{50}+\frac{1}{40}:-\frac{35}{12}=-\frac{67}{50}-\frac{3}{350}=-\frac{236}{175}=-1\frac{61}{175}\).

\(\frac{4}{5}+(-2,8)\cdot(2\frac{1}{3}:2,8-1)=\frac{4}{5}-\frac{14}{5}\cdot\left(\frac{5}{6}-1\right)=\frac{4}{5}+\frac{7}{15}=\frac{19}{15}=1\frac{4}{15}\).

Ответ: а) \(-\frac{2}{9}\); б) \(33\frac{1}{3}\); далее \(-1\frac{61}{175}\) и \(1\frac{4}{15}\).