Answer this question:In two years, Ophelia will be four times as old as Lennon. If Lennon is currently eight years old, how old is Ophelia?
In two years, Lennon will be 2 + 8 = 10 years old. Ophelia will be 4 * 10 = 40 years old in two years. Currently, Ophelia is 40 - 2 = 38 years old.
The answer is 38.

Answer this question:Tommy wants to earn enough money to buy 8 new books. Each book costs $5. If Tommy already has $13, how much does he need to save up?
The books will cost $40 because 8 x 5 = 40. He needs to save up $27 because 40 - 13 = 27.
The answer is 27.

Answer this question:There are 20 boys and 11 girls in the second grade and twice that number in the third grade. How many students are in grades 2 and 3?
There are 20 + 11 = 31 students in second grade. There are 31 x 2 = 62 students in third grade. In total, there are 31 + 62 = 93 students.
The answer is 93.

Answer this question:A frog lays 800 eggs a year. 10 percent dry up, and 70 percent are eaten. 1/4 of the remaining eggs end up hatching, how many frogs hatch out of the 800?

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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Dried up:800(.10) = 80 eggs. 800(.70) = 560 eggs. Total left:800 - 80 - 560 = 160 eggs. 160 / 4 = 40 eggs survive to hatch.
The answer is 40.