A = - 7/5 x 4 /9 = - 28/45
B = - 5/7 x 4/9 = - 20/63
C = - 7 /5 x 9 /4 = - 63 /20
D = - 7/5 x - 4 /9 = 28 /45
- 7/5 x 4 /9 = - 28 /45 donc la A
1 /5 : 5 = 1 /5 x 1 /5 = 1 /25
2/3 : 1/3 = 2 /3 x 3 = 6 /3 = 2
- 3 /7 : - 1 /7 = - 3 /7 x - 7 = 21 /7 = 3
- 8 : 1/8 = - 8 x 8 = - 64
