Your goal is to raise the tip of the obelisk three feet and to support it using as few blocks as possible.
You can locate the fulcrum at one of three points: It is now in the middle location. The mechanical advantage of the lever with the fulcrum here is 1:1. If moved to the left position, the mechanical advantage is 1:3; if moved to the right, 3:1.
Think about where you'd want the fulcrum, then figure out how many blocks you would need to achieve the goal.
By the way, the most efficient builders need a combination of only seven total weights and support blocks.