2.25 square feet
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.
10
288
67 tiles.
2.25 square feet
The answer depends on the measurement units used for 18x18.
220
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.
10
192 tiles
An 18x18 square is equivalent to 324 square feet. This is calculated by multiplying the length (18 feet) by the width (18 feet) to get the total square footage.
288
67 tiles.
118
12...
start with 38 tiles.