If Karen's 128 crayons were twice as many as were in Beatrice's box, there were 128 / 2 = 64 crayons in Beatrice's box. And since Beatrice's box contained twice as many crayons as were in Gilbert's box of crayons, then Gilbert had 64 / 2 = 32 crayons. And since Gilbert had four times as many crayons as Judah, then Judah had 32 / 4 = 8 crayons.
The answer: 8
Reverse engineering the question: Karen had the giant box of crayons, containing twice as many crayons as were in Beatrice's box. But Beatrice's box contained twice as many crayons as were in Gilbert's box of crayons. And Gilbert had four times as many crayons as were in Judah's box of crayons. If Karen's box contained 128 crayons, how many crayons were in Judah's box?


Reasoning and answer: Let M be the number of trees he plants on Monday. On Monday the forest was three times larger from the trees that were originally there and the M trees: 3 * 30 = 30 + M trees. So, 90 = 30 + M. And, M = 60 trees. On Tuesday, he planted 60 trees / 3 = 20 trees. In total, he has planted 60 trees + 20 trees = 80 trees.
The answer: 80
What was the question?
Question: A forester is planting trees. The forest already has 30 native trees. On Monday he triples the number of total trees in the forest by planting new trees. On Tuesday, he plants a third of the amount he planted on Monday. How many trees has the forester planted in total?


The following week, he sold 50 x 3 = 150 kg of salmon. So he sold 50 + 150 = 200 kg of fish.
The answer: 200
Reverse engineering the question: This week, the fishmonger sold 50 kg of salmon. He sold three times more the following week. What was the total amount of fish sold in two weeks?


Reasoning and answer: Nathan added 14 / 2 = 7 blankets to his bed. The blankets warmed Nathan up 7 * 3 = 21 degrees.
The answer: 21
What was the question?
Question: When Nathan is cold, he adds an extra blanket to his bed. Each blanket warms him up by 3 degrees. One night, he was cold enough that he added half of the 14 blankets in his closet on his bed. How many degrees did the blankets warm Nathan up?


Boris' mountain has an elevation 2,500 feet shorter than Hugo's mountain, or 10,000 - 2,500 = 7500 feet above sea level. If Hugo climbed his mountain 3 times, his total climbing distance would be 3 * 10,000 = 30,000 feet. To climb a total of 30,000 feet, Boris would need to need to climb his mountain 30,000 / 7,500 = 4 times.
The answer: 4
Reverse engineering the question: Hugo's mountain has an elevation of 10,000 feet above sea level. Boris' mountain has an elevation that is 2,500 feet shorter than Hugo's mountain. If Hugo climbed his mountain 3 times, how many times would Boris need to climb his mountain to have climbed the same number of feet as Hugo?


The total percentage of money that Reese spent in February and March is 20% + 40% = 60%. This means the April expenses and the money left in her account make up 100% - 60% = 40% of her savings. Reese had $2900 + $1500 = $4400 for the April expenses and the money left in her account. So, $4400 is equal to 40% which means every 1% is equal to $4400 / 40 = $110. Therefore, Reese originally had $110 x 100 = $11000 in her savings account.
The answer: 11000
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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Reese had a sum of money in her savings account. The company she used to work with was not doing well which is why she lost her job. So she spent 20% of her savings for her expenses in February, 40% of it in March, and $1500 in April. How much did she have in her savings account if she still has $2900 after spending those amounts?