Mechanics help please, I am stuck with part d, too many unknowns?

I replied to your other thread about the same question.

You have 3 equations (linearly independent) in four variables. There is one free degree of freedom. Part e) seems to relate this to a matrix/linear system of equations. For this part d), can you use some of the insights you've gained from b) and c) to help you?

In terms of planes etc, you have 3 intersecting 3D planes in 4D space. The intersection should be described by a line involving the 4 variables. Can you manipulate the horizontal, vertical, moment equilibrium equations to find express 3 of the variables in terms of one of them, hence getting the equation of a line?

Thank you for your explanation. I got an equation with 3 of the variables in (Fb1-Fc2-Fc1=0) I don’t understand how to solve for a set of possible solutions.

Can you show how you did it?
In general, there would be many solutions (points lying on the line) and you can't solve uniquely.

It’s a bit messy but here’s my working for d

Yes, I wasn’t completely sure about b but isn’t that the only way for the forces to resolve

I saw that, but why is the moment zero?
You have 3 conditions to satisfy (horizontal, vertical and moment) and you've only considered the first two.

I didn’t consider moment because they’re the only forces that can be used. The moment is zero because there’s no overall moment I think

You have two forces acting at two different points. In general, the body will rotate.
Not sure what you mean by the overall moment.

I give up...