б)6\frac{8}{15}-5= г) 4-\frac{1}{8}= e) 5\frac{1}{9}+2\frac{5}{9}=

б) 6\frac{8}{15}-5 = \frac{6 \cdot 15 + 8}{15} - 5 = \frac{90 + 8}{15} - \frac{5 \cdot 15}{15} = \frac{98}{15} - \frac{75}{15} = \frac{98 - 75}{15} = \frac{23}{15} = 1\frac{8}{15}

г) 4-\frac{1}{8} = \frac{4 \cdot 8}{8} - \frac{1}{8} = \frac{32}{8} - \frac{1}{8} = \frac{32 - 1}{8} = \frac{31}{8} = 3\frac{7}{8}

e) 5\frac{1}{9}+2\frac{5}{9} = \frac{5 \cdot 9 + 1}{9} + \frac{2 \cdot 9 + 5}{9} = \frac{45 + 1}{9} + \frac{18 + 5}{9} = \frac{46}{9} + \frac{23}{9} = \frac{46 + 23}{9} = \frac{69}{9} = 7\frac{6}{9} = 7\frac{2}{3}

Ответ: б) 1\frac{8}{15}; г) 3\frac{7}{8}; e) 7\frac{2}{3}