If 𝐴 is the set of numbers 12, 14, 16 and 𝐵 is the set of odd numbers less than or equal to 17, what is 𝐴 minus 𝐵?
As 𝐵 is the set of odd numbers less than or equal to 17, it will contain the numbers 17, 15, 13, 11, and so on. We know that 𝐴 contains three elements: 12, 14, and 16. These are all even numbers. We’re asked to work out 𝐴 minus 𝐵. And we recall that this means all the elements of 𝐴 that are not elements of 𝐵.
As all three elements of 𝐴 — 12, 14, and 16 — are not elements of 𝐵, the correct answer is 12, 14, 16. In this case, 𝐴 minus 𝐵 is actually equal to 𝐴. This is because none of the elements in 𝐵 exist in 𝐴.