x-0.4x+300=2x/3 两边同时乘以3得
3x-1.2x+900=2x
2x-3x+1.2x=900
0.2x=900
x=900÷0.2
x=4500对不起我搞错了x-0.4x+300=3x/4x-0.4x+300=3x/4 两边同时乘以4得4x-1.6x+1200=3x3x-4x+1.6x=12000.6x=1200x=1200÷0.6x=2000