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Across 2. a set with no elements 4. an amount charged for the use of money 7. a set which contains all elements of all sets being considered in a certain discussion 9. a number that possesses more than two different factors 10. set of all subsets 12. an amount deducted from the original price 14. two fractions that represent the same part of a whole 16. fractions with different denominators 17. a method showing the relationships among sets using a rectangle, which represents the universal set and circles which represents the sets 18. the amount paid to a person or agent for the services rendered

Down 1. a collection distinct objects 2. numbers that are also called counting numbers 3. two sets with exactly the same elements 4. a fraction whose numerator is higher than the denominator 5. a part of a whole 6. equality between two ratios 8. a real number that cannot be expressed as the quotient of two integers 11. a proportion whose change in one produces a corresponding change to the other in the opposite direction 13. the number of elements in a set 15. a natural number that possesses exactly two different factors, itself and one