a)7-3x=28
3x =7-28
3x =-21
x =-21:3
x =-7
b)12-x=13-(-4)
12-x=13+4
12-x=17
x=12-17
x=-5
c)15-2(x-1)=-3
2(x-1) =15+3
2(x-1) =18
x-1 =18:2
x =9+1
x =10
d)2x-(3+x)=5-7
2x-(3+x)=-2
3+x =2x+2
3+x-2 =2x
x+1 =2x
x+1 =x+x
=>x=1
#Chúc bạn học tốt#
k cho mk nha ,please!!!
a) 7 - 3x = 28
3x = 7 - 28
3x = -21
x = -21 : 3
x = -7
vậy x = -7
b) 12 - x = 13 -(-4)
12 - x = 17
x = 12 - 17
x = -5
vậy x = -5
c) 15 - 2 . (x - 1) = -3
2 . (x - 1) = 15 -(-3)
2 . (x - 1) = 18
x - 1 = 18 : 2
x - 1 = 9
x = 9 + 1
x = 10
vậy x = 10
d) 2x - (3 + x) = 5 - 7
2x - (3 + x) = -2
3 + x = 2x -(-2)
3 + x - 2 = 2x
x + 1 = 2x
x + 1 = x + x
=> x = 1
vậy x = 1
k cho mk nha