Applications of systems of linear equations Sorry if this questions is overly simplistic. It's just something I haven't been able to figure out.
I've been reading through quite a few linear algebra books and have gone through the various methods of solving linear systems of equations, in particular, $n$ systems in $n$ unknowns. While I understand the techniques used to solve these for the most part, I don't understand how these situations present themselves. I was wondering if anyone could provide a simple real-world example or two from data analysis, finance, economics, etc. in which the problem they were working on led to a system of $n$ equations in $n$ unknowns. I don't need the solution worked out. I just need to know the problem that resulted in the system.

Here are two neat exmaples I found while researching the topic for a class I'm teaching:
http://www.ohiouniversityfaculty.com/youngt/IntNumMeth/lecture9.pdf (The example deals with systems of equations in statics problems in mechanical engineering; presumably, an introductory text on statics for mechanical engineers might contain more real-life examples by the truckload?)
https://www.researchgate.net/publication/339843126_Balancing_Chemical_Equations_Using_Gauss-Jordan_Elimination_Aided_by_Matrix_Calculator (Just about every introductory [and/or advanced?] chemistry textbook should contain real-life examples by the truckload.)
Hope this helps.
