SOLUTION: Hi guys. On a certain multiple-choice test, 4 points are awarded for each correct answer, and 2 points are deducted for each incorrect or unanswered question. Sally received a t

Algebra ->  Human-and-algebraic-language -> SOLUTION: Hi guys. On a certain multiple-choice test, 4 points are awarded for each correct answer, and 2 points are deducted for each incorrect or unanswered question. Sally received a t      Log On


   



Question 971626: Hi guys.
On a certain multiple-choice test, 4 points are awarded for each correct answer, and 2 points are deducted for each incorrect or unanswered question. Sally received a total score of 84 points on the test. If the test has 30 questions, how many questions did Sally get correct on the test?
Ive manually tried it and I came to the answer of 24. Is there a mathematical equation to solve this?

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = number of correct answers
+30+-+x+ = number of incorrect or unanswered questions
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+4x+-+2%2A%28+30+-+x+%29+=+84+
+4x+-+60+%2B+2x+=+84+
+6x+=+144+
+x+=+24+
Sally got 24 correct
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check:
+4x+-+2%2A%28+30+-+x+%29+=+84+
+4%2A24+-+2%2A%28+30+-+24+%29+=+84+
+96+-+2%2A6+=+84+
+96+-+12+=+84+
+84+=+84+
OK