设大象和牛的体重分别为x(吨)和y(吨),则：8y = x (1)y + 3.5 = x(2)将(2)式代入(1)式,得8y = y + 3.5所以,y = 0.5 将y值(0.5)代入(2)式,得x = 4即：大象的体重为4吨,牛的体重为0.5吨.换算...