0.44444 square feet per tile.
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.
2.25 square feet
You can't answer how many tile you need since the size of the tile wasn't provided in the question. You will need 100 square feet of tile to cover the area and 10 square feet extra for cuts, breaks, and mistakes. Buy 110 square feet of tile.
42
2 square feet per tile.
0.44444 square feet per tile.
About 0.67 sq feet per tile.
Another 53.75 square feet of tile would be needed.
A 24" by 18" tile is 432 square inches or three square feet.
1.78 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.
One square is equal to five square feet.
2.25 square feet
You can't answer how many tile you need since the size of the tile wasn't provided in the question. You will need 100 square feet of tile to cover the area and 10 square feet extra for cuts, breaks, and mistakes. Buy 110 square feet of tile.
1.78 square feet.
About 1.2 square feet x 63 tiles