a, 5.(-8).(-2).(-3)
= [5.(-2)].(-8).(-3)
= (-10).24
= -240
b, 4.(-5).2+2.(-5)-20
= (-5).2[4+(-20)]
= (-10).(-16)
= 160
c, 27.(15-12)-15.(27-12)
= (27.15-27.12)-(15.27-15.12)
= 27.15-27.12-15.27+15.12
= (27.15-15.27)-27.12+15.12
= -27.12+15.12
= 12[(-27)+15]
= 12.(-12)
= -144
d, 3.(-5)^2+2.(-5)-20
= 3.(-5).(-5)+2.(-5)+(-5).4
= 3.(-5).(-5)+(-5).(2+4)
= -15.(-5)+(-5).6
= -5[(-15)+6]
= (-5).(-9)
= 45
e,(15-10)-15.(34-10)
= (15-10)-(15.34-15.10)
= 5-15.34+15.10
= 5+15.[(-34)+10]
= 5+15.(-24)
= 5[1+3.(-24)]
= -355
