Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 我买了一双价值51美元的鞋子。这双鞋已经打了75%的折扣。这双鞋的原价是多少？


### Response:
 假设鞋子的原价为X。打折后的价格为X - X*75% = 0.25 * X = 51美元。
因此 51 / 0.25 = 204 = X。