SOLUTION: After taking 7 quizzes, your average is 78 out of 100. What must your average be on the next 5 quizzes to increase your average to 83? I know the answer is 90 but I have

Algebra ->  Average -> SOLUTION: After taking 7 quizzes, your average is 78 out of 100. What must your average be on the next 5 quizzes to increase your average to 83? I know the answer is 90 but I have      Log On


   

Question 489757: After taking 7 quizzes, your average is 78 out of 100. What must your average be on the next 5 quizzes to increase your average to 83?




I know the answer is 90 but I have no idea how to get to that conclusion! HELP A.S.A.P. PLEASE.
Answer by chessace(471) About Me  (Show Source):
You can put this solution on YOUR website!
x = Ave on next 5.
Final ave = 83 = (7*78 + 5x)/(7+5)