`7,6 : 1,9 . x = 3,2`
`=> 4x = 3,2`
`=> x = 3,4 : 4`
`=> x = 0,8`
`(x - 15).3 : 12 = 6`
`=> ( x - 15 ) . 3 = 6 . 12`
`=> ( x - 15 ) . 3= 72`
`=> x - 15 = 72 : 3`
`=> x - 15 = 24`
`=> x = 24 + 15`
`=> x = 39`
`(x : 4 + 6) . 7 = 70`
`=> x : 4 + 6 = 70 : 7`
`=> x : 4 + 6 = 10`
`=> x : 4 = 10 - 6`
`=> x : 4 = 4`
`=> x = 4 . 4`
`=> x = 16`
