Question 729725
I'll assume one of the 24 feet figures is redundant. 
24*18=432 ft^2 for the floor.
2(24*12)
2*288=576 ft^2 for the 2 larger walls.
2(18*12)
2*216=432 ft^2 for the 2 smaller walls.
432+576+432=1,440 ft^2 for the surface area.
1,440/450=3.2 gallons of paint is required.