The tension in the rope EAB is 850 N. Let T (newtons) denote the tension in the rope ABCD. Then the forces acting on the pulley at B are (i) 850 + T in the direction of A, (ii) T in the direction of C, and (iii) P vertically downwards. If the system is in equilibrium then these forces must balance each other out. So, resolve the forces horizontally to see that . Then resolve them vertically to get . Solve the first equation to find T, then solve the second equation to find P.