algebraic manipulation – Hello, I am trying to solve a linear system using the substitution method, but can’t figure out how to isolate a variable. Please help

I know for the substitution method, I have to isolate the first variable, plug the equation for that variable into the other equations, simplify the new equations, isolate the second variable, etc. I have been trying functions like Reduce and Solve, but they have failed to do so. I’m not sure how else to tackle this problem.

P.S. I know how to do it through LinearSolve and inverse matrix, but I need this one to be solve through substitution method.

Please give me some guidance