Đáp án:
Giải thích các bước giải:
B20:
c) (x-25):3=-8
x-25=-8.3
x-25=-24
x=-24 + 25
x= 1
vậy x = 1
e) 64-3x = 124
3x=64-124
3x=-60
x=-60 : 3
x = -20
vậy x=-20
f)-3x+1=25-32
-3x+1=-7
-3x=-7-1
-3x=-8
x=-8 : (-3)
x= -11
vậy x=-11
g)143-2.(x+1)=-69
2.(x+1)=146-(-69)
2(x+1)= 146 + 69
2(x+1)=215
x+1 = 215 :2
x+ 1= 107,5
x=107,5 - 1
x=106,5
vậy x = 106,5
h)76-5.(3-2x)=181
5.(3-2x)=76-181
5.(3-2x)=105
3-2x=105:5
3-2x=21
2x=3-21
2x=-18
x=-18:2
x=-9
vậy x= -9
B22:
a)(27-7).(-4)+31.(-12-8)
=20.(-4)+31.(-20)
=-20.4+31.(-20)
=-20(4+31)
=-20.35
=-700
b)135+(-241)-135+141
= (135-135)+[(-241)+141]
= 0 + 100
= 100
c) (43-13).(-9)+21.(-16-14)
= 30.(-9)+21.(-30)
=-30.9+21.(-30)
=-30(9+21)
=-30. 30
= -900
d) -(153-170-915)+(15+153-170)
= -15-153+170-153+170+915
= (153-153)+(170-170)+(-15-915)
= 0+0+(-930)
=-930