 Hi and welcome to the session, I'm Asha and I'm going to help you with the following question which says show that if A is a subset of B then C minus B is a subset of C minus A. So first let us learn some simple ideas. First is A is a subset of B which is denoted by S sign if every element of set A is an element of set B and second is A minus B is the difference of set and it contains all those X such that X belong to A and not to B. So with the help of these two definitions we are going to solve the above problem. So this is the idea. Now proceed on with the solution and we are given that A is a subset of B. Let X be any arbitrary element such that it do not belong to set B then this implies X do not belong to set A does this because A is a subset of B and the elements which are not in set B cannot be set A also. Now let us take any arbitrary element which belong to set C minus B this implies that Y belong to set C and Y do not belong to set B this is by the definitions of different set. Now Y do not belong to set B implies Y do not belong to set A also this is from this point this implies Y belong to C and Y do not belong to A this is from here this implies that Y belong to C minus A. So this implies all elements which belong to set C minus B also belong to C minus A and hence the set C minus B is contained in the set C minus A is a subset of B. So this completes the solution hope you enjoyed it take care and have a good day.