Hi learning about set theory but the below question is confusing me a little. I know the question is stating the universal set for all natural numbers below or equal 16 just not sure what its stating for sets A,B,C. Its says x is an element of the universal set such that 2/x?? Is that 'divides'?? or Cardinality?? Or what?? Not sure.

Bit of help would be great.