SOLUTION: At a math contest, 12 problems were given. Five points were awarded for each correct answer, and two points were deducted for each incorrect answer. Matts's score was 39. How many
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Question 1069660: At a math contest, 12 problems were given. Five points were awarded for each correct answer, and two points were deducted for each incorrect answer. Matts's score was 39. How many correct answers did he have? Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! Let x be the number of correct answers and y be the number of incorrect answers, then we have two equations in two unknowns
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1) x + y = 12
2) 5x - 2y = 39
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Solve equation 1) for y
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y = 12 - x
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substitute for y in equation 2)
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5x - 2(12 -x) = 39
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5x - 24 + 2x = 39
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7x = 63
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x = 9
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Matt answered 9 problems correctly
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Check the answer
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y = 12 - 9 = 3
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Substitute for x and y in equation 2)
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5(9) - 2(3) = 45 - 6 = 39
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Our answer checks
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