Question 148518

Let x=score on fourth exam


So the average A of all 4 exams are

{{{A=(73+79+81+x)/4}}}



Since the average must be greater than or equal to 80, this means that the right side is greater than or equal to 80


{{{(73+79+81+x)/4>=80}}} Set the right side greater than 80



{{{73+79+81+x>=320}}} Multiply both sides by 4.



{{{x+233>=320}}} Combine like terms on the left side.



{{{x>=320-233}}} Subtract {{{233}}} from both sides.



{{{x>=87}}} Combine like terms on the right side.



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Answer:


So the answer is {{{x>=87}}} which means that the student must get an 87 or better on the 4th exam.