I'm currently reviewing for a final tomorrow, I need to score a B on the final to stay in school. I'm beginning to panic as I've reviewed all day and have gotten nowhere. 1. The problem statement, all variables and given/known data The tension in the cable AB is 800 lb. Determine the reactions at the fixed support C. 3. The attempt at a solution So I'm basically trying to get a fundamental grasp of these problems and just can't seem to do it. I just need to know the logic behind each step. I have a solution key that is lacking the steps, and the steps are what I need. Firstly, they write out the equation: 800*[(2i-4j-k)/sqrt21]. I'm assuming that these position numbers came from the difference in distance of B from A. But why is it being divided by the square root of 21? And what piece of information does this equation actually give you? Next they write out rCA = 4i + 5k. I assume here they are getting the distance component of the CA beam. The next step, they suddenly have all three component of C figured out. How? Then in the final step, they have the moment figured out for each component of C. Now, I know to get to here from the previous step you'd multiply the magnitudes of the components by the perpendicular distance. Would it be the perpendicular distance from C to A? I assume this because the force is coming out of point A. If anybody could give me clarity on these things, I'd be grateful. I don't know where else to turn.