Then the equation can be established: 48.5x-45.7x=42. At this time, the law of multiplication and distribution can be used, and the formula can be simplified as:

(48.5-45.7)x=42, then: 2.8x=42, then: x= 15, A: I bought 15 basketball and volleyball.

2. There are x copies in the lower layer and 1.5x copies in the upper layer.

Then the equation can be established: 1.5x-20=x+20, and then it can be solved: 0.5x = 40 and x = 80. Answer: The upper layer 120 copies and the lower layer 80 copies.