`a,5.(-8).(-2).(-3)`
`=[5.(-2)].(-8).(-3)`
`= -10 .(-8).(-3)`
`=80.(-3)`
`=-240`
`b,4.(-5).2.(-5)-20`
`=[4.(-5)].[2.(-5)]-20`
`=-20.(-10)-20`
`=200-20`
`=180`
`c,27.(15-12)-15(27-12)`
`=27.15-27.12-15.27+15.12`
`=(27.15-15.27)+12.[(-27)+15]`
`=0+12.(-12)`
`=-144`
`d,1-2+3-4+5-6+...+199-200`
`=(1-2)+(3-4)+...+(199-200)`
`=(-1)+(-1)+...+(-1)`
`=(-1).200`
`=-200`
~ Học tốt ~
#TEAM_IQ_2000