题目某轮船顺水航行3h3h3h,逆水航行1.5h1.5h1.5h,已知轮船在静水中的航行速度是akm/hakm/hakm/h,水流速度是ykm/hykm/hykm/h,轮船共航行多少千米?顺水比逆水多航行多少千米?知识点：整式加减运算法则章节：未标注
