Let us take an example to find range and domain.

Let A = {1,3,5,7} and B = {2,4,6,8,10} and given a relation

R = {(3,2), (5,2), (5,4), (7,2), (7,4), (7,6)}

Now, Domain(R) = {3,5,7}     {if (x,y) is given, then domain contains x value}

and Range(R) = {2,4,6}         {if (x,y) is given, then range contains y value}