1) 10x+7=8x-9
10x-8x=-9-7
2x=-16
x=-8
2) 20-3x=2x-45
2x+3x=20+45
5x=65
x=13
3) 2,7+1,9x=2x+1,5
2x-1,9x=2,7-1,5
0,1x=1,2
x=12
13/18x+13=7/12x+8
13/18x-7/12x=8-13
26/36x-21/36x=-5
5/36x=-5
-180x=5
x=-1/36
1) 10x+7=8x-9
10x-8x=-9-7
2x=-16
x=-8
2) 20-3x=2x-45
2x+3x=20+45
5x=65
x=13
3) 2,7+1,9x=2x+1,5
2x-1,9x=2,7-1,5
0,1x=1,2
x=12
13/18x+13=7/12x+8
13/18x-7/12x=8-13
26/36x-21/36x=-5
5/36x=-5
-180x=5
x=-1/36