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

Решение:

1. \(7\frac{11}{50}+0,78-4\frac{7}{8} = 7\frac{11}{50}+\frac{78}{100}-4\frac{7}{8} = 7\frac{22}{100}+\frac{78}{100}-4\frac{7}{8} = \frac{700+22+78}{100}-4\frac{7}{8} = \frac{800}{100}-4\frac{7}{8} = 8-4\frac{7}{8} = 3\frac{1}{8}\)
2. \(\frac{5}{6}+1\frac{3}{4}+1,25 = \frac{5}{6}+\frac{7}{4}+\frac{5}{4} = \frac{5}{6}+\frac{12}{4} = \frac{5}{6}+3 = \frac{5}{6}+\frac{18}{6} = \frac{23}{6}\)

Ответ: а) $$3\frac{1}{8}$$; б) $$\frac{23}{6}$$.