Find the set four minus the set of numbers one, two, zero, and four.
The first set in this question just contains the number four. We need to subtract the numbers one, two, zero, and four from this set. This means that if the numbers one, two, zero, or four were in the first set, they would need to be removed. As the only number that appears in both sets is four, we need to remove this from the first set.
Removing the only term from the first set leaves us with the empty set. This can be written as the two curly brackets with nothing inside them. Alternatively, we could use the empty set notation, as shown. Subtracting the set of numbers one, two, zero, and four from the set containing just the number four leaves us with the empty set.