You may recall from third semester algebra Cramer's Rule, named for a Swiss mathematician of the 18th century who first discovered this simple way of solving linear equations where the number of unknowns equals the number of equations (a square matrix). Perhaps because of my affinity for the name, it was part of why I had no problem getting an A in third semester algebra. (Math was the only high school class where I would sometimes get a B -- everything else was really easy.)
I was looking for something else, and I happened on this incredibly cute Russian lady explaining how to apply Cramer's Rule to 3x3 matrices. I fear that if she had been teaching me this technique, instead of Mr. Caballero, my high school math teacher, I would have been too distracted to learn.