Coucou, voilà les réponses ^-^, j'espère que ça te sera utile et que tu comprendras :)
[tex]a = ( \frac{1}{2} + \frac{4}{3}) \times \frac{6}{5} \\ = \frac{11}{6} \times \frac{6}{5} \\ = 11 \times \frac{1}{5} \\ = \frac{11}{5} = 2.2[/tex]
[tex]b = - \frac{2}{5} \times ( \frac{2}{7} - \frac{1}{3} ) \\ = - \frac{2}{5} \times ( - \frac{1}{21} ) \\ = \frac{2}{5} \times \frac{1}{21} \\ = \frac{2}{105} [/tex]
[tex]c = ( \frac{5}{8} - \frac{3}{5} ) \times ( \frac{5}{8} + \frac{3}{5} ) \\ = \frac{1}{40} \times \frac{49}{40} \\ = \frac{49}{1600} = {( \frac{7}{40} })^{2} [/tex]
[tex]d = 15 \div ( \frac{1}{4} - \frac{2}{3}) \\ = 15 \div ( - \frac{5}{12}) \\ = - 15 \div \frac{5}{12} \\ = - 15 \times \frac{12}{5} \\ = - 3 \times 12 \\ = - 36[/tex]
