When he gave 40 seashells to his friends, Ali had 180 - 40 = 140 seashells. When he gave another 30 seashells to his brothers, he had 140 - 30 = 110 seashells. He also sold half of the seashells, a total of 1 / 2 * 110 = 55 seashells. He was left with 110 - 55 = 55 seashells.
The answer: 55
Reverse engineering the question: Ali had a collection of seashells. He started with 180 seashells. He then gave away 40 seashells to his friends. He also gave 30 seashells to his brothers. If he sold half of the remaining seashells, how many seashells did he have left?


Reasoning and answer: Cops that served a year pay $85 * 0.2 = $17 less. Cops that served a year pay $85 - $17 = $68. Cops that served at least 3 years get a $68 * 0.25 = $17 discount. Cops that served at least 3 years pay $68 - $17 = $51 for shoes.
The answer: 51
What was the question?
Question: Rookie police officers have to buy duty shoes at the full price of $85, but officers who have served at least a year get a 20% discount. Officers who have served at least three years get an additional 25% off the discounted price. How much does an officer who has served at least three years have to pay for shoes?


He buys 3 * 100 = 300m. So he gets 300 / 10 = 30 sections.
The answer: 30
Reverse engineering the question: John buys 3 reels of 100m fishing line. He cuts it into 10m sections. How many sections does he get?


Reasoning and answer: Michelle kept 4 sandwiches * 2 = 8 sandwiches for herself. This leaves 20 total sandwiches – 4 sandwiches for a coworker – 8 sandwiches for herself = 8 sandwiches for her other co - workers.
The answer: 8
What was the question?
Question: Michelle is bringing sandwiches to work to give to her co-workers. She gives 4 sandwiches to one of her co-workers and keeps twice this amount for herself. If she had originally made 20 sandwiches, how many sandwiches does she have left to give to her other co-workers?


Since the angles in a triangle adds up to 180, and A is 40 degrees, B and C have a total of 180 - 60 = 120 degrees. Since B is two times bigger than C, the total of the angles of B and C is equal to 2C + C = 120. 3C = 120. The angle of C is C = 120 / 3. C is 40. Since B is two times as big as C, B is 2 * 40 = 80 degrees.
The answer: 80
Reverse engineering the question: In a triangle with angles A, B, and C, A is 60 degrees, and B is two times as big as C. Calculate the angle of B.


The pet store has 6 / 2 = 3 cats for sale. They have 6 x 2 = 12 birds for sale. They have 6 x 3 = 18 birds for sale. Therefore, there are a total of 6 + 3 + 12 + 18 = 39 pets for sale.
The answer: 39
Reverse engineering the question:

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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A pet store has six dogs for sale. They have half as many cats, twice as many birds, and thrice as many fish for sale. How many animals are for sale in the pet store?