bài 1
a,2018+(12-2019)
=2018+12-2019
=(2018-2019)+12
=-1+12
=11
b,(-3).92-92.7
=92(-3-7)
=92.-10
=-920
c,567+30:(-3)-(567-654)
=567+30:(-3)-567+654
=(567-567)+654+30:(-3)
=0+654-10
=644
d,345(445-27)-445.345-27
=345.445-345.27-445.345-27
=[(345.445)-(445.345)]-27-345.27
=-27(345+1)
=-27.346
=-9342
bài 2
a,x+25=5
x=-20
vậy x= -20
b,15-2x=-45
2x=-30
x=-15
vậy x=-15
c,(x-3)(-6)+15=3
-6x+18+15=3
-6x+33=3
6x=30
x=5
vậy x=5
