Not possible because the unit of room measure is missing.
However, if one assumes (no old jokes please) that the room measurement is referring to feet, as is typically standard in America, one would calculate:
(11 ft * 12 in per ft ) * (12 ft * 12 in per ft) = 19008 in²
18 in * 18 in = 324 in²
19008 in² / 324 in² = 58.666
This means you would need at least fifty-nine (59) 18*18 in tiles to cover the 11*12 ft room.
As a 18 sq ft room has area equal to 18*144=2592 sq inches, you need 2592/(18*18)=8 18 inch tiles.
1,080 tiles exactly.
A minimum of 33 tiles, a maximum of 40.
875 24-inch tiles.
53 and 1/3 paving slabs exactly.
You will need a minimum of 136 18" x 18" tiles but buy a few extra to account for breakage, etc.
As a 18 sq ft room has area equal to 18*144=2592 sq inches, you need 2592/(18*18)=8 18 inch tiles.
12 tiles by 18 tiles or 216 tiles total
You would need 173 tiles (you would have fractions of tiles left over)
It would be 9 tiles wide by 12 tiles long. That gives you a total of 108 tiles.
1,080 tiles exactly.
360 tiles.
A minimum of 33 tiles, a maximum of 40.
225 16-inch tiles.
875 24-inch tiles.
53 and 1/3 paving slabs exactly.
54 4x4-inch tiles.