SOLUTION: In a mathematics contest,a correct answer gets 100 points while a wrong answer gets a deduction of 40 points.Mike answered all 20 questions and got a score of 180 points.how many w

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Question 1121739: In a mathematics contest,a correct answer gets 100 points while a wrong answer gets a deduction of 40 points.Mike answered all 20 questions and got a score of 180 points.how many wrong answer did he get?
Answer by ikleyn(52914) About Me  (Show Source):
You can put this solution on YOUR website!
.
Let x be the number under the question.


Then the number of correct answers is (20-x),  and your equation is


    100*(20-x) - 40x = 180    (counting points)  ====>


    2000 - 100x - 40x = 180


    2000 - 180 = 140x


    140x = 1820  ====>  x = 1820%2F140 = 13.


Answer.  13 wrong answers and the rest  20-13 = 7 correct answers.


Check.   7*100 - 13*40 = 180 points.   ! Correct !