40/300x-x/5000=0.3解:2/15x-1/5000x=0.32000/15000x-3/15000x=0.31997/15000x=0.3x=0.3÷1997/15000x=4500/1997
40/300x-x/5000=0.32/15x-x/5000=0.32000x/15000-3x/15000=0.31997x/15000=0.31997x=4500x=4500/1997