Final answer:
To achieve an average of 85 over five quizzes, after scoring 90, 85, 95, and 79 on the first four, the student must score at least 76 on the fifth quiz.
Step-by-step explanation:
To determine what a student must score on the fifth quiz to have an average of at least 85, we first find the total points needed for that average over five quizzes. The student seeks an average score of 85 over five quizzes, which total would be 5 quizzes times 85 points per quiz, equalling 425 points.
Next, we sum the scores from the first four quizzes: 90 + 85 + 95 + 79, which totals 349 points. So, we subtract the total points achieved from the total points needed: 425 points (needed) - 349 points (earned) = 76 points. This means the student must score at least 76 on the fifth quiz to attain an average of 85.