Answer:
The approximate cost of a 15-ft-by-18-ft rectangular rug is $729.
Explanation:
It costs a family $324 to buy a 10-ft-by-12-ft rectangular rug.
Means for
square feet, the cost of rug is $324
So, for 15-ft-by-18-ft or
square feet of rug, the cost will be =

Therefore, the approximate cost of a 15-ft-by-18-ft rectangular rug is $729.