GMAT Quantitative Section | Re: Overlapping Sets

Hello everyone,

I very confused with one topic and I hope to find someone who could give me an explanation.

In the Manhattan Guides there are two kinds of Overlapping Sets: 1) Double Set Matix 2) Venn Diagrams
I'm fine with the concept of the two methods but I am confused with further knowledge.

There are also some Algebraic approaches for these methods and I am not sure when I should work with the Matrix or Diagram or when I should use the Algebraic approach.

The algebraic approach for