Answer is 53% when you add 53% to the first 3 grades divide it by 4.. You get 70.5% which is the lowest he can get

# An Arithmetic Student Needs At Least A 70% Average To Receive Credit For The Course. If She Scored 86%, 77%, And 64% On The First Three Exams, What Is The Lowest Score She Can Get On The Fourth Exam To Receive Credit For The Course?

To find the answer you want to add all he problems up and divide them by 3 so you would add 86 plus 77 which =163 plus 64=227 then divide by 3 = 75%