Giải thích các bước giải:
`a)`
`-(12+21-23)-(23-21+10)`
`=-12-21+23-23+21-10`
`=-12-10-21+21+23-23`
`=(-12-10)-(21-21)+(23-23)`
`=-22-0+0`
`=-22`
`b)`
`(57-725)-(605-53)`
`=57-725-605+53`
`=57+53-725-605`
`=(57+53)-(725+605)`
`=110-1330`
`=-1220`
`c)`
`(55+45+15)-(15-55+45)`
`=55+45+15-15+55-45`
`=55+55+45-45+15-15`
`=(55+55)+(45-45)+(15-15)`
`=110+0+0`
`=110`