Réponse :
[tex]A = \dfrac{-27}{7} \times \dfrac{-4}{9}\\A = \dfrac{-27\times (-4) }{7 \times 9}\\A = \dfrac{27\times 4 }{7 \times 9}\\\\A = \dfrac{3 \times 9 \times 4 }{7 \times 9}\\\\A = \dfrac{3 \times 4 }{7}\\A = \dfrac{12}{7}\\\\B = \dfrac{1}{2} : \dfrac{3}{8}\\B = \dfrac{1}{2} \times \dfrac{8}{3}\\B = \dfrac{1 \times 8 }{2 \times 3}\\B = \dfrac{1 \times 2 \times 4 }{2 \times 3}\\B = \dfrac{1 \times 4 }{3}\\B = \dfrac{4 }{3}\\[/tex]
[tex]C = \dfrac{8}{9} : 12\\C = \dfrac{8}{9} : \dfrac{12}{1}\\C = \dfrac{8}{9} \times \dfrac{1}{12}\\C = \dfrac{8 \times 1}{9 \times 12} \\C = \dfrac{4 \times 2 \times 1}{9 \times 4 \times 3} \\C = \dfrac{2 \times 1}{9 \times 3} \\C = C = \dfrac{2}{27}[/tex]
Voilà !
