Area of the rug the family bought = 10 x 12 = 120 ft²
120 ft² cost $234, find the cost of 1 ft²
⇒ 120ft² = $324
⇒ 1ft² = $324 ÷ 120 = $2.70
Area of the new rug = 15 x 18 = 270 ft²
1 ft² = $2.70, find the cost of 270 ft²
⇒ 1 ft² = $2.70
⇒ 270 ft² = 270 x $2.70 = $729
Answer: The 15-ft by 18-ft rug will cost $729