1)2x+9.8-13.6
2x=-9.8+13.6
2x=3.8
x=3.8/2
x=1.9
2)10.36-3x-5.86
10.36-5.86=3x
4.5=3x
x=4.5/3
x=1.5
3)4.2x-6-3.66
4.2x=6+3.66
4.2x=9.66
x=9.66/4.2
x=2.3
4)19.5-0.3x-15.9
19.5-15.9=0.3x
3.6=0.3x
x=3.6/0.3
x=12
5)(7-0.2x)*1.4-7.56
9.8-0.28x-7.56
9.8-7.56=0.28x
2.24=0.28x
x=2.24/0.28
x=8
6) (6.1x-13.2):1.7-3
превращаем в обычную дробь
(61/10x - 66/5): 17/10 - 3
(61/10x - 66/5)* 10/17 - 3
61/17x - 132/17 - 3
61/17x - 183/17 | *17
61x-183
61x=183
x=183/61
x=3