Réponse:
[tex]a = \frac{8}{12} + \frac{5 \times 4}{3 \times 4} = \frac{8 + 20}{12} = \frac{28}{12} [/tex]
[tex]b = \frac{40}{72} - \frac{1 \times 8}{9 \times 8} = \frac{40 - 8}{72} = \frac{32}{72} [/tex]
