x/90-x/(90*1.2)=80/60
问题描述：
x/90-x/(90*1.2)=80/60
答
两边同乘(90*1.2)得
1.2x-x=80*1.8
0.2x=144
x=721.2x-x=80*1.8 1.8哪来的？(90*1.2)/60＝9*0.2 约分得到的，分子80不变对了那1.2x减x呢怎么算呢1.2那来的[x/90-x/(90*1.2)](90*1.2)=(80/60 )(90*1.2)