SOLUTION: An exam has 20 questions. It is scored by giving 10 points for each correct answer and deducting 5 points for every incorrect answer. If you answer all 20 questions and score 125 p

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Question 287832: An exam has 20 questions. It is scored by giving 10 points for each correct answer and deducting 5 points for every incorrect answer. If you answer all 20 questions and score 125 points, how questions did you answer correctly?
a) 15 b) 16 c) 14 d) 11 e) 12
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let a = number of correct answers
Then 20+-+a = number of incorrect answers
given:
10a+-+5%2A%2820+-+a%29+=+125
10a+-+100+%2B+5a+=+125
15a+=+225
a+=+15
20+-+a+=+5
I answered 15 questions correctly
check:
10a+-+5%2A%2820+-+a%29+=+125
10%2A15+-+5%2A%2820+-+15%29+=+125
150+-+5%2A5+=+125
150+-+25+=+125
125+=+125
OK