挖一段水渠,已挖的是未挖的20%,已挖的比未挖的少400米,未挖的多少米?
400÷(1-20%),
=400÷80%,
=500(米);
答:未挖的长度是500米.
因为3x=5y,所以x:y=5:3.______.
This area has been free from Foot-and-Mouth Disease______two years.
A.for B.inC.after D.before