Solution: Let the unit price of A be X yuan, then B is (3X/2) yuan.

The formula is as follows:

[2000/X+ 1000/(3X/2)]* 9 = 1000+2000

Solution: X=8 (yuan)

The second question:

Solution: let a be x kilograms,

The formula is as follows:

20X+ 16 * 10 = 17.5 *( 10+X)

Solution: X=6 (kg)