销售额为附加税除以税率,等于168/（x/100)=16800/x万元;销售量为100-10x万条,且不超过50万条,于是x≥5；根据题意,有销售量×单价=销售额,列方程：(100-10x)×70 = 16800/x整理得,x²-10x+24=0,也即(x-4)(x-6)=0...