Question 925570
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.