George is about to celebrate his 25th birthday. Since his 15th birthday, he's been given a special $1 bill from his parents. They told him that on his 25th birthday, for every bill he still has, they will give him $1.5 in exchange. He spent 20% of his special bills. How much will he receive from his parents when he exchanges them?
Thoughts? Step-by-step reasoning:

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
He received 10 special bills because 25 - 15 = 10. He has 80% of them left because 100 - 20 = 80. He has 8 left because 10 x .8 = 8. His parents will give her $12 for them because 8 x 1.5 = 12.
Thus, the answer is 12.