so dan 1 xa hien nay la 4000 nguoi.
A) voi muc tang hang nam la cu 1000 nguoi thi tang them 21 nguoi hay tinh xem 1 nam sau so dan cua xa do tang them bao nhieu nguoi
B) neu ha muc tang hang nam xuong la cu 1000 nguoi chi tang them 15 nguoi thi sau 1 nam so dan cua xa do tang them bao nhieu nguoi