You can get 20 x 15 = 300 apples per tree. So a total of 300 x 10 = 3000 apples can be gotten from 10 trees.
The answer: 3000
Reverse engineering the question: An apple tree can fill 20 baskets. Each basket can be filled with 15 apples. How many apples can you get from 10 trees?

In the second year, the tree will grow 2 x 1.5 = 3 feet. In the third year, it will grow 3 x 1.5 = 4.5 feet. In the fourth year, it will grow 4.5 x 2 = 9 feet. In the fifth year, it will grow 9 / 2 = 4.5 feet. When the tree is 5 years old, including the first year's growth, it will be this tall 2 + 3 + 4.5 + 9 + 4.5 = 23 feet.
The answer: 23
Reverse engineering the question: A papaya tree will grow 2 feet in the first year. In the second year, it will grow 50% more than the first year. In the third year, the tree will grow 50% more than in the second year. In the fourth year, it will grow twice as much as the third year. In the fifth year, it will grow half as much as the fourth year. When the tree is 5 years old, how tall is the tree?

In each pair of socks there are 2 / 1 = 2 socks. Steve has 2 * 4 = 8 matching socks. Steve has 25 - 8 = 17 mismatching socks.
The answer: 17
Reverse engineering the question: Steve has 25 socks. He has 4 pairs of socks that match, and all the others don't match. How many mismatching socks does Steve have altogether?

The students bought $6 * 20 = $120 worth of tickets. The adults bought $8 * 12 = $96 worth of tickets. Together $120 + $96 = $216 worth of tickets were sold.
The answer: 216
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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Tickets to the school play cost $6 for students and $8 for adults. If 20 students and 12 adults bought tickets, how many dollars' worth of tickets were sold?