Math is fully applicable to repair. I personally applied my knowledge when building my house, when calculating the square footage of rooms, doorways, and other things. Because it can be that you do not correctly calculate the door or window opening and then you do not fit the door or window that you bought.
You're right, it can happen. It is also very important to cooperate with window replacement companies, which calculate in advance all the parameters of your window opening, so that later there would be no problems with its installation. I have always worked and I advise everyone to cooperate with one company Thwindowsdoors. To find out how much windows replacement cost go to this link https://thwindowsdoors.com/window-replacement-cost/. You are welcome.