Résoudre les équations suivantes : 1) x/7=3/5 2) 7-4x=-5+2x 3) 3(4x-9)=-5(4-3x) 4) 3-(2x-7)= x+7

x/7 = 3/5
x fois 5 = 7 x 3
5x = 21
x = 21/5
x= 4,2

7 -4x = -5 +2x
-4x -2x = -5 -7
-6x = -12
x = -12 / -6
x = 2

3(4x-9) = -5(4-3x)
12x -27 = -20 +15x
12x -15x = -20 +27
-3x = +7
x = 7 / -3

3 - (2x-7) = x+7
3 -2x +7 = x +7
-2x -x = +7 -3 -7
-3x = -3
x = -3 / -3
x = 1

 
x* 5 = 7 x 3
5x = 21
x = 21/5
x= 4,2

7 -4x = -5 +2x
-4x -2x = -5 -7
-6x = -12
x = -12 / -6
x = 2

3(4x-9) = -5(4-3x)
12x -27 = -20 +15x
12x -15x = -20 +27
-3x = +7
x = 7 / -3

3 - (2x-7) = x+7
3 -2x +7 = x +7
-2x -x = +7 -3 -7
-3x = -3
x = -3 / -3
x = 1