SOLUTION: On the first 3 tests of his Spanish class, Kevin got an average score of 83. What does he need on the next test to have an overall average of 86?

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Question 490646: On the first 3 tests of his Spanish class, Kevin got an average score of 83.
What does he need on the next test to have an overall average of 86?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
In words:
Average = (total value of items) / (number of items)
Let a = sum of his 3 test scores
Let b = score he needs on next test
given:
(1) ++83+=+a%2F3+
(1) +a+=+249+
(2) +86+=+%28+a+%2B+b%29+%2F+4+
(2) +344+=+a+%2B+b+
Substitute (1) into (2)
(2) +344+=+249+%2B+b+
(2) +b+=+95+
He needs a 95 on the next test