Answer :
[tex]x-\ frade\ from\ next\ test\\\\
\frac{84+65+76+x}{4}=80\ \ \ \ | multiply\ by\ 4\\\\
225+x=320\ \ \ \ | subtract\ 225\\\\
x=95\\\\
He\ should\ have\ 95\ points.[/tex]
the answer would be 95, if you add 95 to the numbers given and divide them by 4 you'll get 80 percent