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U = set of natural numbers less than 8
U = {1,2,3,4,5,6,7,8}
G = set of even integers less than 10
G = {..., -4, -2, 0, 2, 4, 6, 8}
Circle the items in G that are also in set U. Those items are {2,4,6,8}
Then go back to set U = {1,2,3,4,5,6,7,8} and erase 2,4,6,8 to be left with {1,3,5,7}
The complement of a set is everything that isn't in a given set. Think of it as the opposite.