800x+600y=7400, x, y must be a positive integer, x∈,
(2) There are X middle school students and Y primary school students.
X = 1,Y = 1 1,X = 2,Y = 29/3,X = 3,Y = 9,X = 4,Y = 7,X = 5,Y = 17/3。
So * * * has x= 1, y =11; x=3,y = 9; x=4,y = 7; X = 7, y = 3, and * * * are four schemes.