9,8+x=30,8-2x
2x + x = 30.8 - 9.8
3x = 21
x = 7
3x-3,8=x+2,2
3x - x = 2.2 + 3.8
2x = 6
x = 3
4x-4,15=3x+3,81
4x - 3x = 3.81 + 4.15
x = 7.96
6x+14,2=31+5x
6x - 5x = 31 - 14.2
x = 16.8
9,8+x=30,8-2x
2x + x = 30.8 - 9.8
3x = 21
x = 7
3x-3,8=x+2,2
3x - x = 2.2 + 3.8
2x = 6
x = 3
4x-4,15=3x+3,81
4x - 3x = 3.81 + 4.15
x = 7.96
6x+14,2=31+5x
6x - 5x = 31 - 14.2
x = 16.8