Question: Charlotte needs to know how much money to have with her when she goes to the shoe store. How much money should Charlotte bring to buy a pair of boots, if the original price is $90 and there is a discount of 20%?
Answer: The amount of the discount is 20 / 100 * $90 original price = $18. Charlotte needs to bring the $90 - $18 discount = $72. The answer is 72.

Question: Carla spends 10 minutes sharpening her knife and 3 times that amount of time peeling vegetables. How much time does she spend on these activities total?
Answer: First find the total time Carla spends peeling vegetables: 10 minutes * 3 = 30 minutes. Then add the time she spent sharpening her knife: 30 minutes + 10 minutes = 40 minutes. The answer is 40.

Question: Emma traveled by car 280 miles in 2 hours 20 minutes. What was the average speed of the car in miles per hour?
Answer: We first convert the time of 4 hours 20 minutes in minutes 2 hours 20 minutes = 2 × 60 + 20 = 140 minutes. Average speed S is given by distance / time. Hence S = 280 miles / 140 minutes = 2 mile / minute. There are 60 minutes in an hour so the speed is 2 * 60 = 120 miles / hour. The answer is 120.

Question: Jennie makes quilts. She can make 7 quilts with 21 yards of material. How many yards of material would be required to make 12 quilts?
Answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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The amount of material that Jennie needs per quilts is 21 yards / 7 quilts = 3 yards per quilt. In order to make 12 quilts, Jennie will need 12 quilts * 3 yards = 36 yards. The answer is 36.