Have you ever seen a proper Venn diagram with four overlapping circles? No, because it’s impossible. Venn himself discovered this and came up with a clever fix, but this only begot deeper ...

4 + 6 + 8 = 18, the Venn diagram only shows the data of 18 people. Assuming that the given data is correct, there should be 2 people placed inside the rectangle and outside the circles who do not ...