hey guys thanks a million. you both are right. gotta admit im kinda new using mathcad to solve themodynamics problems, i usually use a couple of special excelsheets to solve them, but in this case excel didnt give me a solution. and werner great work on that. the solution found is correct, and thanks for explain it.
but now i got another doubt,i want to use the values of the solution of the problem to find the concentration of the system.
i tried it, but MC use my guess values to calculate it not the ones found.. i have formulate it on the sheet. so if you could check it out it would be great.