1)   8x-3/4=2x-1/4 2)   24/7x+1/14=3/28 3)   2x-3/7=5x-7/2 mrc d'avance !

1 ) 8 x -(3/4) = 2 x -(1/4)

     8 x - 2 x = -(1/4) + (3/4)

   6 x = 2/4 ou 1/2

    x = (1/2) / 6

   x = (1/2) x (1/6)

x = 1/12

2) (24/7) x + (1/14) = 3/28

   (24/7)x  = (3/28) - (1/14)

(24/7) x = (3/28) - (2/28)

(24/7)x = 1/28

 x = (1/28) / (24/7)

x = (1/28) x (7/24) -----------j'ai simplifié (1/4) x (1/24)

x = 1/96

3)  2x - (3/7) = 5x - (7/2)

    -(3/7) = 5x - 2x-(7/2)

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

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

-(6/14) + (49/14) = 3x

(43/14) = 3x

(43/14) / 3 = x

(43/14) x (1/3) = x

(43/42) = x

voilà