x * y = 4950 =(x+ 10)*(9y/ 1 1)
1 1xy=9xy+90y
xy=45y=4950
Therefore, x=45 and y= 1 10.
If the retail price is 9 yuan and the wholesale price is 1 1 yuan, then there are 45 students in this class.
Retail price 1 10 yuan, wholesale price 90 yuan.
When buying 50 pieces, * * * 4500 yuan is the most economical.