x/(x/12+x/15)*(x/12-x/15)=60
问题描述:
x/(x/12+x/15)*(x/12-x/15)=60
答
X/X×(1/12+1/15)×X×(1/12-1/15)=60
X/X×9/60×X×1/60=60
X/9X/60×X/60=60
X×60/9X×X/60=60
60/9×X/60=60
X/9=60
X=60×9
X=540