How to solve this math problem?

There are purple, pink and white cups in Nancy's storeroom. The number of purple cups is 7 times the number of white cups, and there are 20 pink cups. Knowing that the purple cups make up 2/3 of all cups, find the number of the white cups in the storeroom
Asked Aug 19, 2014
Are you able to say how many cups there are total? Like maybe 100 cups total?

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