A shopping mall buys a batch of clothes at the price of A yuan each, and it is stipulated to sell them at the price of B yuan each. On average, 15 pieces are sold every day, and the profit for 30 days is 22,500 yuan.
therefore
(b-a)× 15×30=22500
b-a=50
The mall decided to reduce the price of each piece by 20%, and as a result, it sold 10 pieces on average every day, thus making a profit of 22,500 yuan in 30 days.