x-0.68+3.5=11.3
x=11.3+0.68-3.5
x=8.48
3.5x-x=7.2
2.5x=7.2
x=7.2÷2.5
x=2.88
(x-3.1)=24.8
x=24.8+3.1
x=27.9
5x1.2-2x=4.5
6-2x=4.5
2x=6-4.5
2x=1.5
x=1.5÷2
x=0.75