144 tiles
154
A 3x12 room is 36 square feet. This means that to fill the floor in the 3x12 room, it will take 36 tiles that are each 1 square foot (12x12) in size.
375
If you're talking floor tiles as opposed to wall tiles and by 12x12 you mean they are 12 inches square, then the answer is 300. Because each tile is one square foot and a 15'x20' room is 300 square feet. Simple, eh?
144 tiles
154
A 3x12 room is 36 square feet. This means that to fill the floor in the 3x12 room, it will take 36 tiles that are each 1 square foot (12x12) in size.
13 boxes with 13 tiles in each
168
180
585
If you're talking floor tiles as opposed to wall tiles and by 12x12 you mean they are 12 inches square, then the answer is 300. Because each tile is one square foot and a 15'x20' room is 300 square feet. Simple, eh?
The tile is bigger than the area that you want to cover (12x12 > 10x11) so one tile will do. <><><><><> However, if you meant 12x12 INCH tiles, and a 10x11 FOOT room, you would need 110 tiles.
375
123 will cover it. Get extras.
Since there are no units given it is not possible to answer the question. The units used for measuring the tiles must be different from those used for the room.