Question 460237
you already have an average of {{{(75+86+72)/3=77.7}}}

with the final exam score {{{x}}}:

{{{(75+86+72+x)/4=80}}}

{{{(233+x)/4=80}}}

{{{233+x=320}}}

{{{x=320-233}}}

{{{x=87}}}.....the final exam score should be at least {{{87}}};it could be more, but not less