[Question]Miss Grayson's class raised $50 for their field trip. Aside from that, each of her students contributed $5 each. There are 20 students in her class, and the cost of the trip is $7 for each student. After all the field trip costs were paid, how much is left in Miss Grayson's class fund?
[Answer]The contribution of the students amounted to $5 x 20 = $100. So Miss Grayson's class had $100 + $50 = $150 in all. The cost of the field trip amounted to $7 x 20 = $140. Therefore, the class of Miss Grayson is left with $150 - $140 = $10. The answer is 10.
Q: In a big box, there are marbles in 4 colors. Inside, there are 20 red marbles. There are three times more green marbles than red. Yellow marbles make up 20% of the green marbles. How many marbles are of a different color if the total of all marbles in the box is three times more than the number of green marbles?
A: There are 3 * 20 = 60 green marbles. There are 60 * 20 / 100 = 12 yellow marbles. In total there are 3 * 60 = 180 marbles. That leaves 180 - 20 - 60 - 12 = 88 marbles of another color in the box. The answer is 88.
Question: There are 20 students in the class. Half of them play basketball. Two-fifths play volleyball and one-tenth play both basketball and volleyball. How many students in this class do not play either game?
Answer: Half of the students are playing basketball, which means 20 / 2 = 10 students play basketball. Two - fifths plays volleyball, which leaves us with 20 * 2 / 5 = 8 students. One - tenth play both games, which means 20 * 1 / 10 = 2 students. There are 10 + 8 = 18 students who play basketball or volleyball. Among these 18 students, 2 of them are playing both games, so that means 18 - 2 = 16 students play only one of the two games. So finally, 20 - 16 = 4 students do not play either game. The answer is 4.
[Question]When Jayson is 10 his dad is four times his age and his mom is 2 years younger than his dad. How old was Jayson's mom when he was born?
[Answer]When Jayson is 10 his dad is 10 x 4 = 40 years old. His mom is 40 - 2 = 38 years old. When Jayson is born, his mom is 38 - 10 = 28 years old. The answer is 28.
Q: The file, 90 megabytes in size, downloads at the rate of 5 megabytes per second for its first 60 megabytes, and then 10 megabytes per second thereafter. How long, in seconds, does it take to download entirely?
A: The first 60 megabytes take 60 / 5 = 12 seconds. There are 90 - 60 = 30 remaining megabytes. The remaining 30 megabytes take 30 / 10 = 3 seconds. And 12 + 3 = 15 seconds. The answer is 15.
Question: George donated half his monthly income to charity and spent $20 from the other half on groceries. If he now has $100 left, how much was his monthly income?
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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Half his monthly income is $100 + $20 = $120. His monthly income therefore is 2 * $120 = $240. The answer is 240.