SOLUTION: Mary took 5 English tests. Her scores were 78%, 89%, 98%, 67%, and 90%. What must she score on her sixth test so her average will be 85%?

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Question 154521: Mary took 5 English tests. Her scores were 78%, 89%, 98%, 67%, and 90%.
What must she score on her sixth test so her average will be 85%?
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = score on her sixth test
then to average an 85:
(78+89+98+67+90+x)/6 =85
(422+x)/6 =85
422+x = 510
x = 510 - 422
x = 88