`a, - 4 . ( a + b ) + 4 . a - b`
`= ( - 4 ) . a + ( - 4 ) . b + 4 . a - b`
`= 4 . ( - a ) + 4 . a + ( - 4 ) . b - b`
`= 0 + ( - 4 ) . b - b`
`= ( - b ) . 4 - b `
`= ( - b ) . 5`
`b, 2 . ( - x + 12 ) - 3 . ( x + 1 ) + 5 . x`
`= 2 . ( - x ) + 2 . 12 - 3 . x + 3 . 1 + 5 . x`
`= - 2 . x + 24 - 3 . x + 3 + 5 . x`
`= x . ( - 2 - 3 + 5 ) + ( 24 + 3 ) `
`= x . 0 + 27`
`= 0 + 27`
`= 27`