A building has a symmetric roof made from two straight sections at an angle of 20�‹ above the horizontal. The sides are uniform and have a mass of m = 1800 kg. Find the magnitude of the horizontal force that this roof exerts at the top of the wall, pushing it outward. Before you start your calculation, draw a free body diagram of one side of the roof and label relevant distances.

Im not sure if I even know what it looks like. maybe something like this?:
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Even if it is right, i have no clue on how the forces react in this situation. Please help!

Write moments about the wall top on one half of the building. That will give you the horizontal force pushing on the roof top. The horizontal force on the wall top must be equal and opposite.