The first part of the task is to calculate inner forces within the given section and to draw diagrams of the inner forces for the given construction. Construction is given as a three-hinged frame. Inner forces within the section n-n are calculated using the static equilibrium condition and the method of virtual work. Longitudinal forces, vertical forces, and bending moments are separately calculated. In order to draw the diagrams of inner forces, inner forces are calculated using the static equilibrium condition for every point of the load. The second part of the task is to determine the angles of rotation of the given bodies and the displacements of the given points of a three-hinged frame. Based on the given angle of rotation of the first body, kinematic sizes (angles of rotation and displacements) of the other construction bodies are determined. The task is solved by using displacement diagrams, i.e. by determining the displacement, drawing the known kinematic sizes of a body, constructing the displacement diagrams of the remaining part of the mechanism, and determining kinematic sizes of all bodies from the geometrical conditions. The results are controlled by using the vector calculus.