bài 1:
x: (-2/3) = -5/7
=> x = -5/7 . (-2/3)
=> x = 10/21

(-2/3) : x = 5/6
=> x = -2/3 : 5/6
=> x = -0,8

(-0,75)x = 1/12
=> x = 1/12 : (-0,75)
=> x=-1/9

(-2/7)x = 3 1/21
=> -2/7x = 64/21
=> x = 64/21 : (-2/7)
=> x=-32/3

Bài 1:
a) x : (-2/3) = -5/7
<=> x = (-5/7) . (-2/3)
<=> x = 10/21
b) (-2/3) : x = 5/6
<=> x = (-2/3) : 5/6
<=> x = -4/5
c) (-0,75) . x = 1/12
<=> x = 1/12 : (-0,75)
<=> x = -1/9
d) (-2/7) . x = 3(1/21)
<=> (-2/7) . x = 64/21
<=> x = 64/21 : (-2/7)
<=> x = -32/3

Bài 2:
a) 7/4 . x = 5/6 - 2/3
<=> 7/4 . x = 1/6
<=> x = 2/21
b) 1/2 : x = (-5/7) - (-2/3)
<=> 1/2 : x = -1/21
<=> x = -21/2
c) 4/3 + 5/8 . x = 1/12
<=> 5/8 . x = -5/4
<=> x = -2
d) -2/7 + 2/3 : x = -1/5
<=> 2/3 : x = 3/35
<=> x = 70/9

Bài 3:
a) -5/17 . (3/5 . x - 0,75) = 0
<=> 3/5 . x - 0,75 = 0
<=> 3/5 . x = 0,75
<=> x = 5/4
b) 1/3 . x . (x - 1/6) = 0
<=> x = 0  hoặc  x - 1/6 = 0
<=> x = 0  hoặc  x = 1/6
c) (x + 2)(2x - 4/7) = 0
<=> x + 2 = 0  hoặc  2x - 4/7 = 0
<=> x = -2  hoặc  2x = 4/7
<=> x = -2  hoặc  x = 2/7
d) (2 - 5x)(x + 10/11) = 0
<=> 2 - 5x = 0  hoặc  x + 10/11 = 0
<=> x = 2/5  hoặc  x = -10/11