Let a = {15, 25, 35, 45, 55, 65} and b = {25, 45, 65}. what is a _ b? can someone me

The operation indicated, A - B, is a subtraction of sets.

The subtraction of set B from set A means that you have to remove the elements of B that are on A; i.e. A - B = {15, 35, 55}

25, 45 and 65 (which are in the set B) were removed from the set A to form the set A - B