je donne  15 point a celui qui me fait l'exercice 1  merci

[tex]A= \frac{1}{4} + \frac{5}{6} = \frac{1*6}{4*6} + \frac{5*4}{6*4} = \frac{6}{24} + \frac{20}{24} = \frac{26}{48} = \frac{13}{12} [/tex]

 [tex]B= \frac{2}{7} - \frac{15}{7} * \frac{4}{5} = \frac{2}{7} - \frac{15*4}{7*5} = \frac{2}{7} - \frac{60}{35} = \frac{2}{7} - \frac{12}{7} =- \frac{10}{7} [/tex]

[tex]C= \frac{11}{8} + \frac{14}{18} / \frac{7}{2} = \frac{11}{8} + \frac{14/7}{18/2} = \frac{11}{8} + \frac{2}{9} = \frac{11*9}{8*9} + \frac{2*8}{9*8} = \frac{99}{72} + \frac{16}{72} = \frac{115}{72} [/tex]

[tex]D= \frac{2 ^{3} }{3 ^{2} } * \frac{3}{2 ^{5} } = \frac{8}{9} * \frac{3}{2 ^{5} } = \frac{8}{9} * \frac{3}{32} = \frac{8*32}{9*32} * \frac{3*9}{32*9} = \frac{256}{288} * \frac{27}{288} = \frac{283}{288} [/tex]

Voilà