A choir splits into 3 groups for their performances. The first group has 25 members, and the second group has 30 members. The third group has the remaining members of the choir. If the choir overall has 70 members, how many members are in the third group? Give the rationale and then the answer.
Let's think step by step. There are 25 + 30 members = 55 members in the first two groups. This means the third group has 70 total members – 55 members in the first two groups = 15 members.. The answer is: 15.

Cindy can run at 3 miles per hour and walk at 1 mile per hour. If she runs for half a mile and then walks for half a mile, how many minutes will it take her to travel the full mile? Give the rationale and then the answer.
Let's think step by step. It will take her 0.5 miles / 3 mph * (60 minutes / 1 hour) = 10 minutes to run half a mile. It will take her 0.5 miles / 1 mph * (60 minutes / 1 hour) = 30 minutes to walk half a mile. Her total time is 10 + 30 = 40 minutes.. The answer is: 40.

James needs to get a new pair of glasses. His frames cost $200 and the lenses cost $500. Insurance will cover 80% of the cost of lenses and he has a $50 off coupon for frames. How much does everything cost? Give the rationale and then the 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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Let's think step by step. He gets 500 * .8 = $400 off the cost of lenses. That means the lenses cost 500 - 400 = $100. The frames cost 200 - 50 = $150. So he pays 100 + 150 = $250.. The answer is: 250.