1/
`a)12+2x=−x−|−12|`
`⇔2x+x=-12-12`
`⇔3x=-24`
`⇔x=-8`
`b) (−4)^2 −x=x−2.(−5)`
`⇔16-x=x+10`
`⇔-x-x=-16+10`
`⇔-2x=-6`
`⇔x=3`
2/
`a) −81.43+81.143`
`=81*(-43+143)`
`=81*100=8100`
`b)77.91+(−77).(−9)`
`=77(91+9)`
`=77*100`
`=7700`
`c)15.84−35.(−84)`
`=84(15+35)`
`=84*50`
`=4200`
`d)−63.83−63.17`
`=-63(83+17)`
`=-63*100`
`=-6300`
3/
`a)142.(16+42)+(−42).(16+142)`
`= 142 . 58 - 42 . 158`
`= 1600`
`b)59.(41−89)+41.(−89−59)`
`= 59 . (-48) + 41 . ( -148 )`
`= -8900`
`c) −77.(52+23)+23.(77−52)`
`= -77 . 75 + 23 . 25`
`= -5200`
`d)(−45).(55−24)+(−55).(−45−24)`
`=-45 . 31 - 55 . ( - 69 )`
`=2400`