If A = $\left\{ 2,4,6,8,10,12 \right\}$ and B = $\left\{ 3,4,5,6,7,8,10 \right\}$ find:
(a). A – B
(b). B – A
(c). $\left( A-B \right)\cup \left( B-A \right)$

Hint: First we will write the definition of union, intersection and we will also give the meaning of subtraction of two sets and after that we will substitute the value of A and B in the given options and find it’s value.

Complete step-by-step answer:

Union: The union (denoted by $\cup $ ) of a collection of sets is the set of all elements in the collection. It is one of the fundamental operations through which sets can be combined and related to each other.
Intersection: The intersection of two sets has only the elements common to both sets. If an element is in just one set it is not part of the intersection. The symbol is an upside down $\cap $ .
When we subtract two sets the common elements of the set which is being subtract is removed and the remaining elements is the final answer.
Let’s solve each part one by one:
For (a), we have
A – B =$\left\{ 2,12 \right\}$
Hence this is the answer for (a).
For (b), we have
B – A = $\left\{ 3,5,7 \right\}$
Hence this is the answer for (b).
For (c), we have
A – B =$\left\{ 2,12 \right\}$
B – A = $\left\{ 3,5,7 \right\}$
Now we get that $\left( A-B \right)\cup \left( B-A \right)$ will be,
$=\left\{ 2,3,5,7,12 \right\}$
Hence this is the answer for (c).

Note: We have used the fact that how the two sets are subtracted and also the definition of the given terms are also useful. One must memorize the definition so that there can be no mistake in the future. This is a simple question and so the chance of making silly mistakes in a hurry to solve it are also higher.