Answer:
Step-by-step explanation:
[tex]average= \frac{sum of scores}{number of tests}[/tex]
[tex]80= \frac{79+81+77+x}{4}[/tex]
80 x 4 = 79+81+77+x
320=237 + x
320-237 = x
83=x
so Marianne must score 83 points or higher on her last test
