Here is a rotational equilibrium problem
Note that you use both translational and rotational equilibrium! Also, you can pick your axis of rotation, so why not choose a location to eliminate unknown torques.
Here is the classic “ladder problem” – and they show a different way to calculate torques: instead of multiplying the perpendicular component of the force by the distance it acts at, you can multiply the entire force by the perpendicular distance between that force and the axis of rotation. It’s the same math, but sometimes easier to visualize on a diagram: