Find the set of element 51 minus the set of element 15.
So we want to take any elements that are in this set and that are also in this set and subtract it from the first set. But, the only element in the first set is 51. And the only element in the second set is 15. So since there’s only the element 15 in the second set, there’s nothing to subtract from the first set because there is no 15 in the first set. So our answer will be the set of element 51.
A similar example would be having a set of elements two, four, and five. And then subtracting the set of elements three, four, five. So since we are subtracting an element four and there is an element four in the first set, we take it away. And same thing with five. We take it away. So what’s left in the first set would be two.
So in our example of the 51 minus 15, since there wasn’t anything in common to subtract, our answer was just that first set, the set of element 51.