It is two parallel equations with two unknowns xy. The solution is to get a relationship about xy and then substitute it for the solution.

The coordinate formula means that the small items are independent of each other, and the calculation error of one small item will not affect the other. The conditions in the general question stem can be called, while the conditions in each small question can only be called in this small question, but it is independent, not absolute, because many ways of thinking can be continued, especially some questions from special to general structure.