Đáp án:

Giải thích các bước giải:

 `a)`

` x + 2/9 = 1 1/2 - 7/9 `

` x + 2/9 = 13/18 `

` x = 13/18 - 2/9 `

` x = 1/2 `

Vậy ` x = 1/2 `

``

`b)`

` - 13/15 + x = - 3/8 - (- 4)/5 `

` - 13/15 + x = - 3/8 + 4/5 `

` - 13/15 + x = 17/40 `

` x = 17/40 + 13/15 `

` x = 31/24 `

Vậy ` x = 31/24 `

``

`c)`

` - 8/13 + ( - 7/5 - x ) = - 1/2 `

` - 7/5 - x = - 1/2 + 8/13 `

` - 7/5 - x = 3/26 `

` x = ( - 7/5 ) - 3/26 `

` x = - 197/130 `

vậy ` x = - 197/130 `

``

`d)`

` - 1 1/7 - [ - 5/3 + ( x - 7/3 ) ] = - 4/21 `

` - 5/3 + ( x - 7/3 ) = ( - 1 1/7 ) - ( - 4/21 ) `

` - 5/3 + ( x - 7/3 ) = - 8/7 + 4/21 `

` - 5/3 + ( x - 7/3 ) = - 20/21 `

` x - 7/3 = - 20/21 + 5/3 `

` x - 7/3 = 5/7 `

` x = 5/7 + 7/3 `

` x = 64/21` 

Vậy ` x = 64/21` 

``

`e)`

` - 2/3 - x : 1/2 = 2/5 `

` x : 1/2 = ( - 2/3 ) - 2/5 `

` x * 2 = - 16/15 `  

 ` x = - 16/15 : 2 `

` x = - 8/15 `

Vậy ` x = - 8/15 `

``

`f)`

` - 1 3/5 * x - 4/9 = - 1/3 `

` - 8/5 * x = - 1/3 + 4/9 `

` - 8/5 * x = 1/9 `

` x = 1/9 : ( - 8/5 ) `

` x = - 5/72 `

Vậy ` x = - 5/72` 

``

`g)`

` - 4/5 * x - ( 0,25 - x ) = - 13/3 `

` - 4/5 * x - 0,25 + x = - 13/3 `

` ( - 4/5 + 1 ) * x - 0,25 = - 13/3 `

` 1/5x - 0,25 = - 13/3 `

` 1/5x = - 13/3 + 0,25 `

` 1/5x = - 49/12 `

` x = - 245/12 `

Vậy ` x = - 245/12 `

``

`k)`

` ( 12/7 : x - 0,5 ) ( 2/5 * x - 1 1/2 ) = 0 `

` 12/7 : x - 0,5 = 0 ` hoặc ` 2/5 * x - 1 1/2 = 0 `

``

`TH1`

` 12/7 : x - 0,5 = 0 `

` 12/7 : x = 0,5 `

` x = 24/7 `

``

`TH2`

` 2/5 * x - 1 1/2 = 0 `

` 2/5 * x = 1 1/2 `

` x = 15/4 `

Vậy ` x = 24/7` hoặc ` x = 15/4 `