Problem Solving
试题详情
题目：
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 used only Brand B soap. How many of the 200 households surveyed used both brands of soap?
选项:
A、15
B、20
C、30
D、40
E、45
答案:
A
提问：
and for every household that used both brands of soap, 3 used only Brand B soap. 这句话啥意思？
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