24解:(比七年级有学生(45x+55)名年级有学生(55x+30y)名(2)(45145)+(5x+30y)=(100485)名所以七、八年级共有学生(100x+45y)名(3)当x4,y=6时,100x+85=100×4+85×6=910(名)所以当x4y=6时,该