Given:
Frank knows that his first four test grades were 74, 76, 77, and 84
We will find Frank's grade on the fifth test if his test average is 80.6.
So, let the fifth grade = x,
The average is the sum of the grades over the number of the grades
So,
[tex]\frac{74+76+77+84+x}{5}=80.6[/tex]Solve the expression to find x:
[tex]\begin{gathered} 74+76+77+84+x=5\cdot80.6 \\ 311+x=403 \\ x=403-311=92 \end{gathered}[/tex]So, the answer will be: the fifth grade = 92
