Bonjour

a.

7/5 x - 4/9 = - 28/45

- 5 x 2/3 = - 10/3

- 28/27 x 36/7 = - 1 008/189 = (63 x - 16) / (63 x 3) = - 16/3

b.

0,15/2,6 x 3,9/0,45 = 0,585/1,17 = (0,585 x 1 000) / (1,17 x 1 000) = 585/1 170 = (585 x 1) / (585 x 2) = 1/2

- 33/7 x - 21/25 x - 15/44 = 693/175 x - 15/44 = - 10 395/7 700 = (385 x 27) / (385 x 20) = 27/20

- 3/4 x 8 x 7/9 = - 24/4 x 7/9 = - 6 x 7/9 = - 42/9 = (3 x - 14) / (3 x 3) = - 14/3.