A: x-5 sur 4= 4 sur 3                                         D:1 sur 3-x= - 2 sur 9 B: x+ 7 sur 3=5 sur 7                                        E: 5 sur 18-x=

Bonsoir

A: x-5 sur 4= 4 sur 3   
A = x -5/4 = 4/3
A = 12x/12 - 15/12 = 16/12
A = 12x = 16 +15
A = 12x = 31
x = 31/12

B = x+ 7 sur 3=5 sur 7       
x +7/3 = 5/7
21x + 49 = 15
21x = 15 -49
21x = 34
x = 34/21               

 C: x- 5 sur 8= 3 sur 12   
C = x -5/8 = 3/12
C = 24x - 15 = 6
C = 24x = 6 +15
24x = 21
x = 21/24 = 7/8

D:1 sur 3-x= - 2 sur 9
1/3 - x = -2/9
3/9 - 9x = -2
-9x = -2 -3
-9x = -5
x = 5/9

E: 5 sur 18-x=11 sur 45
5/18 - x = 11/45
25/90 - 90x = 22/90
-90x = 22 - 25
-90x = - 3
x = 3/90 = 1/30

F: x -12 sur 25= -11 sur 15
F = x -12/25 = - 11/15
75x/75 - 36/75 = - 55/75
75x = -55 +36
75x = - 19
x = -19/75