12. A merchant in Lishui Department Store sells two kinds of goods, A and B, and the price of each kind of goods is the same. When a commodity is sold, the merchant can make a profit of 25% and sell i

12. A merchant in Lishui Department Store sells two kinds of goods, A and B, and the price of each kind of goods is the same. When a commodity is sold, the merchant can make a profit of 25% and sell it. Solution: (1) loss, 3 yuan;

(2) Let the purchase price of commodity A be X yuan and that of commodity B be Y yuan.

From the meaning of the question: x( 1+25%)=a,

x=a，

x= a，

y( 1-20%)=a，

y=a，

y= a，

That is 2a-( a+ a)=2a- a=- a,

Lose one yuan.

(3) There are five A's and two B's, (the answer is not unique, it satisfies 5n A's and 4n-2 B's, and n is a positive integer. )