求各位大神来解答一道数学题

天才大泽

A marketing firm determined that,of 200 households surveyed ,80 used neither Brand A nor Brand B soap,60 used only Brand A soap ,and for every household that used both brands of soap ,3 uesd only Brand B soap .How many of the 200 household surveyed used both brands of soap .       a 15     b 20     c   30  d  40  e 45  答案选择a   15  不解 希望高人指点

ClaudiaJL

translation→只使用B的家庭的数量是两个牌子都用的家庭数量的3倍

set x为同时使用Brand A & B
80+60+x+3x=200
x=15

719331003

应该是20吧

天才大泽

非常感谢你的解答

天才大泽

答案是15见二楼的解答