1.9x=3+8x
8x-1.9x=-3
6.1x=-3
x=-30/61
2.3x+45=63
2.3x=63-45
2.3x=18
x=18÷2.3
x=7又19/23
3.4x+35=80
3.4x=80-35
3.4x=45
x=45÷3.4
x=13又4/17