[Question]: Yuan is 7 years older than his brother David and twice his age. How old is David?
[Answer]: Let x be David's age. Yuan is seven years older than David, 7 + x = Y years. Yuan is also twice David's age, 2 * x = Y years. Since these two equations equal the same thing, we can write: 7 + x = 2 * x. Subtracting x from both sides we get 7 = x, so David is 7 years old.
So the answer is 7.

[Question]: Jackson's oldest son gets 4 cookies after school and his youngest son gets 2 cookies after school. If there are 54 cookies in a box, how many days will the box last?
[Answer]: The oldest son gets 4 cookies and the youngest gets 2, so every day they eat 4 + 2 = 6 cookies. There are 54 cookies in a box and the boys eat 6 cookies a day, so the box will last 54 / 6 = 9 days.
So the answer is 9.

[Question]: One barnyard owl makes 5 hoot sounds per minute. If 5 less than 20 hoots per minute are heard coming out of the barn, how many Barnyard owls would this noise be coming from?
[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
5 less than 20 hoots per minute is 20 - 5 = 15 hoots per minute. If one barnyard owl makes 5 hoot sounds per minute, then 15 hoots per minute are coming from 15 / 5 = 3 barnyard owls.
So the answer is 3.