a) `-25.72+25.21-49.25`
`= 25.(-72)-25.21-49.25`
`=25.[(-72)+21-49]`
`=25-100`
`=-2500`
b) `35.(14-23)-23.(14-35)`
`=35.14-23.35-(23.14-23.35)`
`=35.14-23.35-23.14+23.25`
`=(35.23-23.35)+(35.14+23.14)`
`=14.12`
`=168`
c) `27.(13-16) - 16 . ( 13 - 27 )`
`=27.13-27.16-(16.13-16.27)`
`=27.13-27.16-16.13-16.27`
`=13.(27-16)+0`
`=13.11+0`
`=143`
d) `32 . (-39) + 6 . (-22)`
`=16.2(-39)+6(-22)`
`=16.(-78+22)`
`=22.[(-72)+(-28)]`
`=22.(-100)`
`=-2200`