SOLUTION: Manuel's quiz scores in history are 76, 81, and 77. What score must he get on his fourth quiz to have an average of at least 80?

Question 925570: Manuel's quiz scores in history are 76, 81, and 77. What score must he get on his fourth quiz to have an average of at least 80?
Answer by wrodriguez50(1) (Show Source): You can put this solution on YOUR website!
Given: 76, 81, 77
Solve for Avg >= 80
The variable "x" is Manuel's score on the fourth quiz
(76 + 81 + 77 + x)/4 >= 80
Multiply both sides by 4 to get rid of the fraction
76 + 81 + 77 + x >= 320
Combine like terms
234 + x >= 320
Subtract both sides by 234 to get "x" alone
234 - 234 + x >= 320 - 234
X >= 86
Therefore, Manuel needs to score 86 or better on his next quiz to have an average of at least 80.

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