1)8x-21=3x+9
5x-30 = 0
5x = 30
x = 6
2)10-x=12x+40
-13x-30 = 0
13x+30 = 0
13x = -30
x = -30/13
х=-2,30769230769
3)9x-10=x+14
8x-24 = 0
8x = 24
x = 3
4)3x-7=x+14
3x-7=x+14
2x-21 = 0
2x = 21
x = 21/2
х=10,5
1)8x-21=3x+9
5x-30 = 0
5x = 30
x = 6
2)10-x=12x+40
-13x-30 = 0
13x+30 = 0
13x = -30
x = -30/13
х=-2,30769230769
3)9x-10=x+14
8x-24 = 0
8x = 24
x = 3
4)3x-7=x+14
3x-7=x+14
2x-21 = 0
2x = 21
x = 21/2
х=10,5