[tex]a)\\\\8\frac{6}{13}-6\frac{11}{13}=7\frac{19}{13}-6\frac{11}{13}=1\frac{8}{13}\\\\b)\\\\8\frac{3}{8}+4\frac{5}{6}=8\frac{9}{24}+4\frac{20}{24}=12\frac{29}{24}=13\frac{5}{24}\\\\c)\\\\9\frac{4}{5}-7\frac{2}{3}=9\frac{12}{15}-7\frac{10}{15}=2\frac{2}{15}\\\\d)\\\\1\frac{4}{21}*4\frac{4}{5}=\frac{\not{25}^5}{\not{21}^7}*\frac{\not{24}^8}{\not{5}^1}=\frac{40}{7}=5\frac{5}{7}[/tex]
[tex]e)\\\\6\frac{8}{9}:5\frac{1}{6}=\frac{62}{9}:\frac{31}{6}=\frac{\not{62}^2}{\not{9}^3}*\frac{\not{6}^2}{\not{31}^1}=\frac{4}{3}=1\frac{1}{3}[/tex]
