Answer: The carpet will cost $72
Explanation: Area of the carpet that will cover the room is calculated by: A = length x width.
A = 12*18 = 216 square feet
The price is given per square yard. So to transform square feet in square yard:
1 square ft = 0.111 square yard
216 = 216 / 9 = 24 square yard
To carpet the room, it will be needed 24 square yard of a carpet.
Since 1 square yard costs $3:
24*3 = 72
The cost to carpet a 12x18ft room is $72.