Question: Hendricks buys a guitar for $200, which is 20% less than what Gerald bought the same guitar for. How much did Gerald pay for his guitar?
Answer: Let G be the price Gerald paid for his guitar. Then 0.8 * G = $200. So G = $200 / 0.8 = $250. The answer is 250.
[Question]At a certain car dealership, 15% of the cars cost less than $15000 and 40% of the cars cost more than $20000. If there are 3000 cars at the dealership, how many of them cost between $15000 and $20000?
[Answer]15% of 3000 cars is (15 / 100) * 3000 = 450 cars. 40% of 3000 cars is (40 / 100) * 3000 = 1200 cars. 450 + 1200 = 1650 cars which cost either less than $15000 or more than $20000. Out of 3000 cars, there will then be 3000 - 1650 = 1350 cars left which cost between $15000 and $20000. The answer is 1350.
Q: Jacob can write twice as fast as Nathan. Nathan wrote 25 letters in one hour. How many letters can the two write in 10 hours together?
A: Since Nathan writes 25 letters in an hour, Jacob writes 25 * 2 = 50 letters in an hour. Together, they write 50 + 25 = 75 letters in an hour,. In 10 hours, they'll write a total of 75 * 10 = 750 letters. The answer is 750.
Question: Thomas made 4 stacks of wooden blocks. The first stack was 7 blocks tall. The second stack was 3 blocks taller than the first. The third stack was 6 blocks shorter than the second stack, and the fourth stack was 10 blocks taller than the third stack. If the fifth stack has twice as many blocks as the second stack, how many blocks did Thomas use in all?
Answer: The second stack has 7 blocks + 3 blocks = 10 blocks. The third stack has 10 blocks - 6 blocks = 4 blocks. The fourth stack has 4 blocks + 10 blocks = 14 blocks. The fifth stack has 10 blocks x 2 = 20 blocks. In total there are 7 blocks + 10 blocks + 4 blocks + 14 blocks + 20 blocks = 55 blocks. The answer is 55.
[Question]Aziz's parents moved to America in 1982. The year is 2021 and Aziz just celebrated his 36th birthday. How many years had his parents been living in America before Aziz was born?
[Answer]Aziz was born in the year 2021 - 36 years = 1985. Therefore, Aziz's parents had been living in America for 1985 - 1982 = 3 years. The answer is 3.
[Question]At the beginning of an academic year, there were 15 boys in a class and the number of girls was 20% greater. Later in the year, transfer students were admitted such that the number of girls doubled but the number of boys remained the same. How many students are in the class now?
[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.
user
The original number of girls was 20% greater than 15 (the number of boys) giving 15 + (20 / 100) * 15 = 18. After the admission of transfer students, the number of girls doubled to become 18 * 2 = 36. In addition to the 15 boys, there are now 15 + 36 = 51 students in the class. The answer is 51.