67 tiles.
288
It is not clear what is meant by an "18x18 square feet" tile. 18ft * 18 ft = 324 square feet, so that one tile will be more than enough. An 18 inch by 18 inch tile cannot be a 18x18 square feet tile.
The answer will depend on the units used for measuring the tiles which you have failed to specify.
3
67 tiles.
start with 38 tiles.
192 tiles
288
118
It is not clear what is meant by an "18x18 square feet" tile. 18ft * 18 ft = 324 square feet, so that one tile will be more than enough. An 18 inch by 18 inch tile cannot be a 18x18 square feet tile.
12...
The answer will depend on the units used for measuring the tiles which you have failed to specify.
18" x 18" = 1.5' x 1.5' = 2.25 square feet90/2.25 = 40 tiles.
22.2 tiles so buy 23 tiles.
The answer depends on the measurement units used for 18x18.
220