Question 765737


Let {{{x}}} = score on the 5th quiz to have an {{{80}}} average

if first four quizzes are {{{83}}}, {{{72}}}, {{{89}}}, {{{78}}}, then

{{{(83+72+89+78+x)/5=80}}} .....solve for {{{x}}}

{{{83+72+89+78+x=80*5}}}

{{{322+x=400}}}

{{{x=400-322}}}

{{{x=78}}}.... she must score {{{78}}} to have an average of {{{80}}}