题目

One day Mrs White took Trudy and Ben to go shopping. They went to the supermarket in the new shopping mall(购物中心).Why do you buy things here, Mum? Trudy asked. Because they are cheaper than those at the corner store, Mrs White said. Help me check(检查) the prices. The Whites were not wealthy(富有的) and Mrs White was always careful with her money. She looked carefully at the prices of things. She bought some groceries(杂货) in the supermarket. When they got home, the children said, We don't think you saved money by going to the supermarket there. Of course I did, sa如果把+210元表示收入210元，那么-60元表示________．