①5x-3=3x-1+2-2x
5x+3=x+1
4x=-2
x=-1/2
②3x-1+2-2x=1.2-2.7x
x+1=1.2-2.7x
3.7x=0.2
x=0.054054
③5x-3=1.2-2.7x
7.7x=4.2
x=0.545455
楼主.实在不知道了.纯手打.