标题: 数学问题~~~~ [打印本页] 作者: 徐小涵 时间: 2013-10-30 15:05 标题: 数学问题~~~~ A marketing firm determined that of 200 households surveyed, 80used neither Brand A nor Brand B soap,60 used only Brand A soap. and for every household that used both brands of soap,3 used only Brand B soap. How many of the 200 households surveyed used both brands of soap?
