The Bridge Structure stage forming liner governing equation solution

I need the procedure to get the result of the linear governing equation.
2. Here are provided with the attached file, the method, and the result. I need to understand how they calculate and get results.
3. As you can see the picture 5 they use this equation to solve the problem.
4. Pictures 1, 2, 3, 4, 7, and 8 are the problem and data.
5. I have attached the Pdf file, where gives the whole description and problem and result. I just need to understand the procedure of calculation and get results.
6. If “EI” and “EA” value is and “α” Change then what will be happened with results. And there have 10 elements if the element will increase then what happened?