Problems of this type can be solved in several ways. In this movie, two approaches will be demonstrated. First, a trial-and-error approach will be used to determine the maximum allowable load P. Then, a more algebraic approach that works very well on simpler problems will be used.

The figure shows a diagonal member labeled 1 and a horizontal member labeled fixed to a column on the right at the points A on top and C below. The diagonal member runs between points A and B and the horizontal 
member runs between the points B and C. Joint B is at a distance of 4.3 meters to the left of A and 5 meters below A. Joint C is 
at a distance of 7 meters directly below A. The load at joint B is labeled P and it is directed downwards.