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}.