I was triying to resolve this ecuation with "Maxima",But i dont now how to make it work,I have 2 vector with unkown components(0,y,z) and (0,g,n),and 2 forces with components unkown,but proporcional.¿
¿How can i resolve this kind of system?

Hoja de trabajo4.sm (139 KiB) downloaded 65 time(s).

Here I have calculated the force resultant and decomposed in different directions, at several places.
No time to explain the details, but if you like you can use some of those methods.
It's just an application of the classic method.
There is some graphic representation of both forces and structural members, also.

Patharpratima Community Centre wind calculations 4-3-2022.sm (842 KiB) downloaded 54 time(s).

Hoja de trabajo4.sm (148 KiB) downloaded 47 time(s).

Oh my god it's a 3D system of forces. If you want to solve in 3D you will get screws/wrenches, it's terribly complicated to resolve. I did once in geogebra, it works but it's so involved I didn't have the courage to translate to Smath. A more elegant way than solving 3D screws would be to work with polar polyhedra (see the PhD of Marina Konstantatou). I also did that in geogebra, and here also, couldn't find teh courage to translate to Smath. But it would be very exciting if someone could do that, because geogebra is very limited in the size of data it can handle because of its interactive mechanism.

So anyway, for a practical solution, in your place I would work in 2D projections of the 3D forces. 2 projections are enough. It's absolutely fine for engineering purposes in my (limited) experience.

https://www.geogebra.org/m/vkzdc68w
https://www.geogebra.org/m/es2abqgd
https://www.geogebra.org/m/euy4yaqw
https://www.geogebra.org/m/fdmgsqyy
Some practical examples and some useful academic references for solving forces in 3D

Hola Erre. You can have a lot of issues trying to solve your system with maxima because that the decomposition over components isn't automatic in SMath.

In the attached a numerical method implemented for solve the system, which depends of the guess value, as usually do any numerical method.

Hoja de trabajo4.sm (151 KiB) downloaded 44 time(s).
Hoja de trabajo4.pdf (536 KiB) downloaded 51 time(s).

Best regards.
Alvaro.