三分之一/(三分之二-五分之二)*五分之三
=(1/3)/(2/3-2/5)*3/5
=3/(15*(2/3-2/5))
=3/(10-6)
=3/415哪来的？三分之一/(三分之二-五分之二)*五分之三=(1/3)/(2/3-2/5)*3/5=(1/3*3/5)/(2/3-2/5)=(3/15)/(2/3-2/5)=3/(15*(2/3-2/5))=3/(10-6)=3/4