Question 628886
Suppose a student has earned the following grades on her first four quizzes:
 83, 72, 89, 78.
 What must she score on her fifth quiz in order to have a mean of 80 on all of her quizzes?
:
Let x = score on the 5th quiz to have an 80 average
:
{{{(83+72+89+78+x)/5}}} = 80
Multiply both sides by 5 and solve for x