Réponse:
[tex]n10).....a = \frac{5}{6} + \frac{7}{8} = \frac{40 + 42}{48} = \frac{82}{48} = \frac{41}{24} \\ b = \frac{ - 4}{7} - \frac{3}{5} = \frac{ - 20 - 21}{35} = \frac{ - 41}{35} \\n11)......a = \frac{ - 3}{20} - \frac{5}{12} = \frac{ - 36 - 100}{240} = \frac{ - 136}{240} = \frac{ - 17}{30} \\ b = \frac{7}{9} - \frac{ - 3}{8} = \frac{56 + 27}{72} = \frac{83}{72} \\ n12)......a = \frac{15}{10} + \frac{ - 2}{15} = \frac{175 - 20}{150} = \frac{155}{150} = \frac{31}{30} \\ b = \frac{15}{ - 9} + \frac{1}{15} = \frac{175 - 9}{ - 135} = \frac{ - 166}{135} [/tex]
