Structural mechanics and truss supports

Man, I am seriously struggling with these kinds of problems and it’s driving me nuts. Has anyone here actually figured this stuff out? Like, is there anyone who can walk me through the logic without making my head explode? Here is an example of one of the assignments I'm stuck on 🙂

Honestly, it’s all a bit of a mess right now, so I’d say just aim for the Math and Science track.
😬