a)`(7× x+8):9= 4`
`7× x+ 8 =4×9`
`7× x+ 8 =36`
`7× x = 36-8`
`7× x = 28`
` x = 28 : 7`
` x = 4
` Vậy` ` x=4`
b) ` 7/5-2/5 × x = 1 `
` 2/5 × x = 7/5 - 1`
` 2/5 × x = 2/5`
`x = 2/5 : 2/5`
` x = 1`
` Vậy` ` x = 1`
c)`( 6/5:3/5+1) × x- 6 × 3/2015=6×2012/2015`
`(6/5 . 5/3+1) × x- 18/2015 = 12072/2015 `
`(2+1) × x = 12072/2015 +18/2015`
`3 × x = 6`
` x = 6:3`
` x = 2`
`Vậy` ` x = 2`