三楼那个文明点他还是小孩别代坏了5x+7=42 5x=42-7 5x=35 x=35除以5 x=7
5x+7=425x=42-75x=35x=7
方程两边都-7 5x=35,方程两边都÷5 x=7.
5x+7=42 5x=42-7 5x=35 x=7
5x=42-75x=35x=7
