90. Выполните действия: a) 7\frac{11}{50}+0,78-4\frac{7}{8}; 6) \frac{5}{6}+1\frac{3}{4}+1,25.

a) $$7\frac{11}{50}+0,78-4\frac{7}{8} = 7\frac{22}{100}+\frac{78}{100}-4\frac{7}{8} = 7\frac{1}{5}+\frac{39}{50}-4\frac{7}{8} = 7\frac{40}{200}+\frac{156}{200}-4\frac{175}{200} = 7\frac{196}{200}-4\frac{175}{200} = 3\frac{21}{200}$$

Ответ:$$3\frac{21}{200}$$

б) $$\frac{5}{6}+1\frac{3}{4}+1,25 = \frac{5}{6}+1\frac{3}{4}+\frac{125}{100} = \frac{5}{6}+1\frac{3}{4}+\frac{5}{4} = \frac{5}{6}+1\frac{3}{4}+1\frac{1}{4} = \frac{5}{6}+3 = 3\frac{5}{6}$$

Ответ:$$3\frac{5}{6}$$