What are common mistakes students make with Cramer's rule?
The mistakes I'm aware of that most students do is not evaluate the determinants correctly. They make mistakes with determining the co-factors with the proper signs. And then, most of them don't verify the answers by substituting the values of variables into the given equations and checking whether the values have been consistent with the equations or not. Other than that, Cramer's rule is too simple to make any other mistake.