1, if the sales of two sizes of clothes are the same. Then, after the calculation, the supermarket will lose money. Because that dress lost 20%, and the cost should be 100 yuan; Earn 20% of the cost of clothes should be 67 yuan. If the sales volume is the same as N, then the supermarket should lose a total of -7n yuan.

2. It is different to sell less clothes at a loss and sell more clothes at a profit. You have to calculate according to the specific method. As mentioned above, you first find out the difference between the original clothing cost and the actual seller, and then multiply it by their respective sales quantity.