`a)`
`8/15x + 5/7 = -2/21`
`=> 8/15x = -2/21 - 5/7`
`=> 8/15x =-17/21`
`=> x= -17/21 : 8/15`
`=> x = -85/56`
Vậy `x=-85/56`
`b)`
`2/3 . (3x-2) + 25% . x = -9/6`
` => 2x - 4/3 + 1/4 x = -9/6`
`=> 2x + 1/4x = -9/6 + 4/3`
`=> 9/4x = -1/6`
`=> x= -1/6 : 9/4`
`=>x = -2/27`
Vậy `x=-2/27`
`c)`
`3,2x - (4/5 + 2/3) : 11/3 = 7/20`
`=> 3,2x - 22/15 : 11/3 = 7/20`
`=> 3,2x - 2/5 = 7/20`
`=> 3,2x = 7/20 + 2/5`
`=> 3,2x = 3/4`
`=> x = 3/4 : 3,2`
`=> x = 15/64`
Vậy `x=15/64`
`d)`
`(3/5x - 2/3x - x) . 1/7 = -5/21`
`=> 3/5x - 2/3x - x = -5/21 : 1/7`
`=> x (3/5 - 2/3 -1) = -5/3`
`=> -16/15 .x = -5/3`
`=> x = -5/3 : (-16)/15`
`=> x = 25/16`
Vậy `x=25/16`
