so dan o mot xa hien nay co 4000 nguoi
a,voi muc tang hang nam la cu 1000 nguoi thi tang them 21 nguoi hay tinh xem mot nam sau so dan cua xa do tang them bao nhiu nguoi
b,neu ha muc tang hang nam xuong la cu 1000 nguoi chi tang them 15 nguoi th sau mot nam so dan cua xa do tang them ba nhieu nguoi