To find the dimensions of the room we have to factor the expression:

To do this we need to find to factor for 3 and 4. For three we have the options 3 and 1, for 4 we have the options 2 by 2. Then we cross multiply this factors, in this case we get 2*2=6 and 2*1=2. Since the sum is 8 that means that:

Therefore the dimensions of the rectangle are (3x+2) and (x+2).
Now, if x=2 then the area of the room is:

Therefore the area is 32 squared feet.
If each square feet cost $4.49 to tile then the total cost will be:

Therefore it will cost $143.68 to tile the floor.