SOLUTION: I've been working on this problem for a long time but i just can't seem to find the answer could you please help me. thank you. Susan's average score for her fist three psychology

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Question 123017This question is from textbook Algebra for College students
: I've been working on this problem for a long time but i just can't seem to find the answer could you please help me. thank you.
Susan's average score for her fist three psychology exams is 84. what must she get on the fourth exam so that her average for the four exams is 85 or better? This question is from textbook Algebra for College students

Answer by rapaljer(4671) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = grade on fourth exam
+%2884%2B84%2B84%2Bx%29%2F4=85

Mult both sides by 4:
+84%2B84%2B84%2Bx=340
252%2Bx=340
x=340-252=88

R^2

P.S. An easier way to do this is to realize that if you need an 85 average, and your grades are below 85 by 1 point on each of 3 exams, then you need an 85 on the last test, plus 3 points (to make up the shortfall on the first 3 exams), for a total of 88.