Answer: {4,5,6}
Step-by-step explanation: Sets could be explained as a representation of elements which could be numbers, alphabets or a collection of items which are wrapped inside a curly bracket {}. Generally in mathematical or statistical parlance, once elements are wrapped around curly braces, the collection of those emmts is called a set. And therefore, set arithmetic such as union, intersection, complement e.t.c can be performed on elements of the given set. Elements wrapped in curly braces signifies that the elements reperesents an entire entity.
In the question given above, {7,8,9} reperesents a set containing three elements : 7, 8,9.