50/1.5x-50/2.5x=1
100/3x-20/x=1
100-3*20=3x
3x=40
x=40/3
两边先约分再去分母即可.
【欢迎追问,】(x/y-y/x)÷(x/y+y/x-2)×(1+y/x)其中x=1/2，y=1/3(x/y-y/x)÷(x/y+y/x-2)×(1+y/x)=(x^2-y^2)/(x^2+y^2-2xy)*(x+y)/x=(x+y)(x-y)/[(x-y)^2]*(x+y)/x=(x+y)^2/[x(x-y)]=(5/6)^2/[1/2*(1/2-1/3)]=(25/36 )/(1/12)=25/3