In mathematics, a set is a collection of numbers. They are displayed in brackets and a comma is used to separate each number. For example, a set is displayed in the following way: {3, 5, 4, 6}. Sets are also displayed visually with the use of a Venn diagram. This is useful for showing the intersections between two sets of numbers. Subtracting a set of numbers from another involves removing all numbers that intersect between the two sets. This subtraction is also possible with the use of a calculator that has a "Set" key.

Set up the equation as follows, where "a," "b," "c" and "e" are variables representing numbers:
{a, b, c}  {a, c e}
In this example, we are subtracting a set of three numbers from another set of three numbers.

Remove any numbers from the first set that overlap with the set that you are subtracting. In the example {a, b, c}  {a, c e}, the variables "a" and "c" are removed.

Write the remaining numbers from the first set as the set that remains after subtraction. For this example, the answer is: {b}. If the sets are reversed and the equation is {a, c e}  {a, b, c}, the answer is: {e}.
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