Basically, you have a rod kept horizontally on three supports. It's in equilibrium. The positions of the supports and the mass and length of the rod are given. Find the normal force by each support. The problem looks particularly simple. But notice that you have a shortage of an equation. You have three things to find - the three normal forces. And you have only two equations - one for translational equilibrium of the rod and one for the rotational equilibrium. So what's the problem? I asked this at several places and they blatantly said that the system is not solvable. But to me, non-solvability means non-uniqueness. I am not able to understand how is the system non-unique. Am I not providing all the required information? It's also surprising that the same set of information works properly with a two support system. What's happening in the transition from two to three?