When a system is in equilibrium, 2 conditions are met.
1) Principle of Moment (POM):
Sum of anticlockwise moment = Sum of clockwise moment
2) Net force = 0N; all forces are balanced:
Total downward forces = Total upward forces
Whenever a force passed through the pivot point, that force will not create any moment as there is no perpendicular distance from the force to the pivot. Hence this force will not be included in the calculation of moments.