89. Найдите значение выражения: a) $$6\frac{3}{4}-2\frac{1}{6}$$; б) $$9\frac{8}{15}-4\frac{1}{12}+3\frac{7}{20}$$; в) $$7\frac{5}{8}+3\frac{2}{3}-8\frac{3}{16}$$

Решение:

1. \(6\frac{3}{4}-2\frac{1}{6} = \frac{27}{4}-\frac{13}{6} = \frac{81}{12}-\frac{26}{12} = \frac{55}{12}\)
2. \(9\frac{8}{15}-4\frac{1}{12}+3\frac{7}{20} = \frac{143}{15}-\frac{49}{12}+\frac{67}{20} = \frac{572}{60}-\frac{245}{60}+\frac{201}{60} = \frac{528}{60} = \frac{44}{5}\)
3. \(7\frac{5}{8}+3\frac{2}{3}-8\frac{3}{16} = \frac{61}{8}+\frac{11}{3}-\frac{131}{16} = \frac{976}{128}+\frac{473}{128}-\frac{1048}{128} = \frac{401}{128}\)

Ответ: а) $$\frac{55}{12}$$; б) $$\frac{44}{5}$$; в) $$\frac{401}{128}$$.