Maths venn diagrams

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Across
  1. 4. all members of all sets
  2. 7. a series of overlapping circles
  3. 8. when 2 sets overlap
  4. 9. a set within a set
Down
  1. 1. not A'
  2. 2. a whole number
  3. 3. something that belongs to a set
  4. 4. everything in all sets
  5. 5. a collection of items
  6. 6. what A,B,C,D... are