`25-(30+x)=x-(27-8)`
`<=> 25 - 30 - x = x - 27 + 8`
`<=> -5 - x = x - 19`
`<=> -x - x = 5 - 19`
`<=> -2x = -14`
`<=> x = 7`
-------------------------------------
`(x-12)-15=( 20 - 7 ) - ( 18 + x )`
`<=> x - 12 - 15 = 20 - 7 - 18 - x`
`<=> x - 27 = -5 - x`
`<=> x+ x = 27 - 5`
`<=> 2x = 22`
`<=>x = 11`
-----------------------------------------
`x + ( 17 - 8 ) = 5 + ( 10 - 3x )`
`<=> x + 17 - 8 = 5 + 10 - 3x`
`<=> x + 9 = 15 - 3x`
`<=> x + 3x = -9 + 15`
`<=> 4x = 6`
`<=> x = 3/2`
----------------------------------------------
` 3( x - 3 ) - ( x + 1) = 12`
`<=> 3x - 9 - x - 1 = 12`
`<=> 2x -10=12`
`<=> 2x=22`
`<=> x=11`
-------------------------------------
`4( x - 1 ) - 2( x + 3 ) = 26`
`<=> 4x-4-2x-6=26`
`<=> 2x-10=26`
`<=> 2x=36`
`<=> x=18`