Answer:
70
Step-by-step explanation:
mean = sum of all / number of quizzes
x = the remaining student's score
(2(30) + 1(30) + 3(80) + x)/8 = 50
[multiply each side by 8]
2(30) + 1(30) + 3(80) + x = 400
[simplify]
60 + 30 + 240 + x = 400
330 + x = 400
[subtract 330 from each side]
x = 70
