In our Linear Algebra class we barely touched on (and I mean barely touched up on) circuits. Thing is, it will be on the exam, but just 1 question. My problem is understanding how to get the formula to use Cramer's Rule Of course I know how to set these up into Matrices and do all of that. But my issue is how do they get these formulas? Why is E1 positive and E2 negative Why is R2 (Ia - Ib) but on the other it's (Ib - Ia) Any help is appreciated. I'm not asking for a problem to be solved. Just need sort of a lesson on how to read these sorts of images.