There appears to me to be one important piece of information missing! How wide is each hallway? The two far side walls have length 60 y and height 9 feet= 3 yards so that area (ignoring doors, etc. for the moment) is 3(60)= 180 square yards. The "bottom" wall has length 90 y and height 3 y so its area is 3(90= 270 y. But the problem is the "inside walls". The two inside walls on the side have length 60 y minus the width of the bottom hall- which we are not given. Similarly the length of the inside wall of the bottom hall is 90 y minus two times the width of each side hall. You need to multiply the lengths of those walls by the 3 yard height to get their areas. Once you have the total wall area, subtract the total area of the doors, etc. But you really need to know the width of the halls.