以下两例分别取材于实际生活的节水问题和个人所得税的问题 ,它能通过建立恰当的数学模型使问题获解 ,是考查建模能力的好题 .但遗憾的是一些参考解答的建模不够合理 ,甚至由于建模不合理出现解答错误的情况 .本人认为此类应用题宜建立不等式模型解之 .例 1　为加强公民的节水 The following two cases are based on the problems of water saving and personal income taxation in real life. It can solve problems by establishing appropriate mathematical models. It is a good question to examine the modeling capabilities. However, unfortunately, some reference solutions are modeled. It is not reasonable, even if the model is unreasonable, there is a case where the answer is wrong. I think that such an application should be solved by establishing an inequality model. Example 1 To enhance the water saving of citizens