9,8+x=30,8-2x;3x-3,8=x+2,2;4x-4,15=3x+3,81;6x+14,2=31+5x​

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