The mean is the sum of all numbers divided by the number of numbers. We can set up an equation:
[tex]\sf\dfrac{78+81+69+94+x}{5}=79[/tex]
Where 'x' is the next quiz score she need. Solve for 'x'. Multiply 5 to both sides:
[tex]\sf 78+81+69+94+x=395[/tex]
Add:
[tex]\sf 322+x=395[/tex]
Subtract 322 to both sides:
[tex]\boxed{\sf x=73}[/tex]
So her next quiz score needs to be 73 in order to have a mean score of 79 on all her quizzes.
