问题描述: tell me what you see give me the answer . 1个回答 分类:英语 2014-09-30 问题解答: 我来补答 12/7x+9/7x=21/7x=3xI think that you could understand this clearly,the both fractions have the common denominator,the addtion of the two numerators is 21.21/7x=3x. 展开全文阅读