Which of the following sets is closed under subtraction?

Integers are closed under subtraction because subtracting any integer from another always gives an integer; for example, 3 − 8 = −5. Whole numbers and natural numbers are not closed under subtraction, since subtracting a larger number from a smaller one can give a negative result. Irrational numbers are not closed either, since √2 − √2 = 0, which is rational.

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