一、方程组与应用题列方程组解应用题是把“未知”转化为“已知”的重要方法,它的关键是把已知量和未知量联系起来,找出题目中的相等关系.一般来说,有几个未知量就必须列出几个方程,所列方程必须满足:方程两边表示的是同类量;同类量的单位要统一;方程两边所表示的数量要 First, equations and application of problem equations The solution of equations is an important method to convert “unknown” to “known”. The key is to associate the known quantity with the unknown quantity to find the problem. Equivalence relations. In general, there are several unknowns that must be listed in several equations. The listed equations must satisfy: The equations on both sides represent the same type of quantity; Units of the same type must be unified; The quantities expressed on both sides of the equation must be