`a)8 - ( 21 - x ) = 16 `
`→8-21+x=16`
`→-13+x=16`
`→x=16+13`
`→x=29`
`b)- 25 + ( -16 + x ) = 0 `
`→-25-16+x=0`
`→-41+x=0`
`→x=41`
Vậy `x=41`
`c)- 51 - ( 17 - x ) = 0 `
`→-51-17+x=0`
`→-68+x=0`
`→x=68`
Vậy `x=68`
`d)26 - ( x - 5 ) = 32 `
`→26-x+5=32`
`→31-x=32`
`→-x=31-32`
`→-x=-1`
`→x=1`
Vậy `x=1`
`e)( x - 15 ) - ( x + 21 ) + ( x -11 ) = 7`
`→x-15-x-21+x-11=7`
`→(x-x+x)+(-15-21-11)=7`
`→x-47=7`
`→x=7+47`
`→x=51`
Vậy `x=51`