本文将九年义务教育三年制初级中学教科书《代数》第一册（上）第232页第2题“有含盐15％的盐水20千克，要使盐水含盐10％，需要加水多少千克？”的6种解法介绍如下，供同学们参考：解1设需要加水X千克，则根据加水前后纯盐不变的关系列出方程：答：需要加水10千克．解2设需要 This article will be nine-year compulsory education three-year primary school textbooks “Algebra” Volume I (top) page 232 Question 2: "Salt 15% salt water 20 kg, to salt water 10%, the amount of water needed to add kilograms The six solutions of “?” are described below for reference of the students: Solution 1 needs to add X kg of water, then the equation is listed according to the relationship between pure salt before and after adding water: A: It needs to add 10 kg of water. Solution 2 needs