We need to find the area of the hallway. To find the area of a rectangle, simply multiply the length and width together.
6ft * 18ft = 108^ft
Now, let's find the area of the square tiles. To find the area of a square, simply square one side.
(2/3ft)^2 = 4/9ft^2
To find out how many square tiles are necessary to tile the hallway, lets divide the area of the hallway by the area of one square.
108ft^2 / (4/9ft^2) = 243 tiles